I tend to disagree with
Gone_Jackel. We have sources indicating that up to a certain stage Hecate was indeed perceived as a beneficient Goddess.
Hesiod (in whose writings she is first mentioned) praised her in the
Theogony at length (she gets more space than any other deity save the
Muses), as a beneficient deity who aids her devotees, without being modern:
"...Hecate, whom Zeus the son of Cronos honoured above all. He gave her splendid gifts, to have a share of the earth and the unfruitful sea. She received honour also in starry heaven, and is honoured exceedingly by the deathless gods. For to this day, whenever any one of men on earth offers rich sacrifices and prays for favour according to custom, he calls upon Hecate. Great honour comes full easily to him whose prayers the goddess receives favourably, and she bestows wealth upon him; for the power surely is with her. For as many as were born of
Earth1 and Ocean2 amongst all these she has her due portion. The son of Cronos did her no wrong nor took anything away of all that was her portion among the former Titan gods: but she holds, as the division was at the first from the beginning, privilege both in earth, and in heaven, and in sea. Also, because she is an only child, the goddess receives not less honour, but much more still, for Zeus honours her. Whom she will she greatly aids and advances: she sits by worshipful kings in judgement, and in the assembly whom she will is distinguished among the people. And when men arm themselves for the battle that destroys men, then the goddess is at hand to give victory and grant glory readily to whom she will. Good is she also when men contend at the games, for there too the goddess is with them and profits them: and he who by might and strength gets the victory wins the rich prize easily with joy, and brings glory to his parents. And she is good to stand by horsemen, whom she will: and to those whose business is in the grey discomfortable sea, and who pray to Hecate and the loud-crashing Earth-Shaker3, easily the glorious goddess gives great catch, and easily she takes it away as soon as seen, if so she will. She is good in the byre with Hermes to increase the stock. The droves of kine and wide herds of goats and flocks of fleecy sheep, if she will, she increases from a few, or makes many to be less. So, then, albeit her mother's only child, she is honoured amongst all the deathless gods. And the son of Cronos made her a nurse of the young who after that day saw with their eyes the light of all-seeing Dawn4. So from the beginning she is a nurse of the young, and these are her honours."*
In the Homeric Hymn to Demeter, she is the only Goddess willing to help the grief stricken Demeter look for her daughter, Persephone, who was kidnapped by Hades. She is refered to as "tender-hearted Hecate"*. Because of her help to Demeter "from that time the lady Hecate was minister and companion to Persephone."*
In Hesiod's time there was a large cult devoted to Hecate in Ionia (Hesiod's parents immigrated to Boeotia from Ionia), and appearantly his father was a member of this cult. Hesiod's brother was named Persaeus after Hecate's father.
In addition, throughout Antiquity Hekates deipnon (Hecate's dinner) was celebrated in the 30th of each month, and on that day every rich person had to leave a meal (and a good one at that) at the feet of Hecate's public statues inside the cities, so that beggars and paupers could take them home without having to go through the actual humiliating begging.
Hecate was always associated with the moon as well as the dead and magic, and in the Hellenistic era she gradually started to be regarded as vindictive and sometimes even evil, associated closely with witchcraft (as can be seen in Theocritus's idylls) and the Erinyes. But she always remained a strongly personal deity with protective qualities.
Christianity intensified the perception of Hecate as evil, making her a demonic Queen of the Witches, as a part of the Christian general attempt to demonize all the gods of Greece and Rome.
I was rather astonished to read some of the details of your response, some are quite bizzare, coming from anyone who knows anything about Ancient
Greece.
To call Hesiod "a lone 8th century poet" is at best misleading. Hesiod is the earliest Greek poet to have anything of his writings survive (except Homer). In fact he is the ONLY 8th century poet we know anything of. But all that aside, what's more important is the way he was perceived in Antiquity, and the truth is that other than Homer, Hesiod was the closest thing the Greeks had to Holy Scriptures. Everybody, anywhere in Greece read him, and everybody, anywhere in Greece were educated on his writings. Every man in Greece knew by hard extensive parts of Hesiod's Theogony and Erga kai Hemerai, as well as the two other poems attributed to him (The Shield of Herakles and The Catalogue of Women), in that sense they were as widely known as the Iliad and the Odyssey. Furthermore, since Homer completely ignores the Chthonic deities and traditions (and Hecate is by all means such a deity), Hesiod was the primary source for the Greeks themselves on these things.
As for your second claim that Hecate "is neither inherently beneficent nor vindictive", that is true regarding any Greek god. The Greeks didn't have our notion of the goodness of god. To the Greeks the gods were capricious and selfish most of the time. They aided when it was convenient and harmed whenever they wanted to. This fact defined the very relationship between men and gods in Antiquity: the mortals worshipped the gods so as not to give them reason to be angry at them, and perhaps to encourage them to help them. When Chryses prays to Apollo in the first poem of the Iliad he uses the imperative, commanding the god to attend and listen to his prayer (this is described as a magical ritual, rather than as a prayer in the monotheist way), and Apollo must comply because Chryses reminds him of all the things he's done for the god throughout the years (built him temples and sacrificed hecatombs), by those deeds he's gained the right to summon and command the god to be present, further request may appear in the optative to signify a more polite request, after the initial contact was established by command. As a contrast to Chryses' addressing of the god, we have, several lines earlier, his addressing Agamemnon (in a request to free his captured daughter). This request is entirely in the optative and it is emphatically different from the later addressing of the god.
This is the reason that the Greeks worshipped actively only gods who could benefit them. Impartial deities such as the Moira (or in plural Moirai), or Hades, were not worshipped. There are no temples for these deities anywhere in Greece (although Pausanias mentions once a temple to Hades in the northern Peloponnese, it has not yet been discovered, and many archaeologists doubt Pausanias' testimony). The fact that Hecate was indeed worshipped is a strong indication that people expected her to benefit them. As for your claim that I have not yet established that her worship was not apotropaic, I don't have to. Regardless of whether it was or not, it still makes her beneficient.
As for Hecate and magic, true, any god had his share of magic (what the Romans called numen) in his own field of control, but very early on in the Greek tradition it became Hecate's role to observe magic that was performed by mortals. She is Medea's patroness already in evidences from the 6th century BC, Aristophanes and Euripides regard her as the mistress of all witches, and in Theocritus' second idyll ("The Sorceress") there are elaborate descriptions of a young woman who prays for Hecate to aid her in her attempt to cast a spell over her lover who's dumped her for another, so that he'd come back to her (I've not yet seen a poem in which he actually describes the goddess herself, either as "the big bad witch" or otherwise, if you know of such a place, please send me notice it'd be most interesting), there are detailed descriptions of the entire process of casting the spell as well as the preperations for it.
The question we're discussing here is basically mythological, and as mythology is, by definition, a literary tradition, I rely mainly on literature. Religion (that is the actual practices or rituals etc.), is a completely different matter, and you'd often find contradictions between religion and mythology (whether ancient Greek, Roman, Jewish or Christian). Hera, who is ever the great mother and wife in mythology was worshipped in some places as Hera Parthenos (Hera the virgin). Zeus, who in religion is the protector of law, commits quite a few transgressions of law in mythology. Artemis, the virgin goddess, was worshipped in Ephesos as a primitive and very sexual fertility goddess, whose symbol were human testicals. Religion has nothing to do with the character of a god. Besides I never said that Hecate wasn't associated with the dead, quite the contrary, which you'd know if you read what I wrote above. This alone did not make her baneful in Greek eyes, up to a very late stage. What I said was that she became synonymous with death and evil witchcraft only with Christianity.
As for the Ostrakismos, I am once again astounded (perhaps it is you that needs some extensive reading, and I'm talking basic introductory textbooks, you seem to need them). The unique thing about Ostrakismos is that it was never any sort of punishment and was never associated with pollution. It was a unique Athenian institution, that was meant to solve political stagnasis (or attempts to establish sole-rule) by sending one political leader to temporary exile without damaging his reputation, or implying anything about his demeanor or behaviour, was certainly not connected with pollutions of any kind, and after that 10 year period passed he could return to Athens and resume his former life. What you perhaps mean (and it is quite astounding that you, as someone who claims to have knowledge of Greek history, and who have written some quite good factual nodes on the subject, would confuse the two), are punishments of exile (not the Ostrakismos!!!!) that people who performed religious offenses (including murder, sacrilege etc.) were sentanced to. Those punishments indeed were involved with pollution, as the Greeks believed that to allow such a man to walk unharmed was to incurr the wrath of the gods (cf. Oedipus), but again you seem to confuse the terminology. Those who were sentanced to exile had to leave not only the asty (the physical city), but the polis (the political unit that is controlled by a city), not all the territory of any polis was urban, quite the contrary, (The Athenian polis included Attica, the thinly populated isle of Salamis and starting with the 5th century BC also the isles of Imbros and Lemnos), and not everything that was located outside a city (thus 'excluded' from it) was unholy, in fact the holiest sites for the Greeks (Olympia and the Oracle of Delphi) were located outside cities (though both belonged to poleis: Olympia to Elis and the Oracle to Delphi). Therefore not everything lacated outside cities is "polluted" including the crossroads on which Hecate (in cooperation with Hermes btw) kept. And besides the Hekates deipnon was conducted inside cities (thus 'included' in them).
*
The quotes were taken from "The Online Medieval and Classical Library" in the Berkely digital library at http://sunsite.berkeley.edu/OMACL/
1 Gaia or Ge, the goddess who is a personification of the earth.
2 Oceanus or Okeanos, the god who is a personification of the river that surrounds the earth.
3 Epithets of Poseidon
4 Eos, the goddess who is a personification of dawn, and the messenger of the gods.