The first rule of thumb when dealing with ancient Greek mythology: Fate is not a nice lady. In fact she's … well… she's not nice. You might think of her as the Simon Cowell of the ancient Greek world; even if she passes you on to the next round of American Idol, she does so by poking you with a stick. Mythological characters that fall on her good side often resent her for the junk they have to go through to reach their destiny, and characters that fall on her bad side usually wind up dead or in prison.
Hesiod's Theogony faces us with a blunt example of the futility (not-worth-it-ness) of trying to avoid Fate. Cronus is made aware almost from the moment he ascends the throne that he's going to lose it eventually. The moment that the prophecy is revealed, Cronus begins taking steps to avoid his destiny, chomping down divine babies one after another. But in spite of his efforts, events still play out exactly as they were foretold. This is a firm constant in ancient Greek literature: nobody gets to avoid their destiny, not even the gods. (Except for Zeus, who basically gets to do whatever he wants.)
But the Theogony also presents us with a unique picture of Fate when compared to later myths. You see, ancient Greek culture had a number of representations for the idea of fate. The most recognizable of these is the three Moirae, "the fates," who you'll be familiar with if you've seen Disney's Hercules or the remake of Clash of the Titans. The fates were three ugly, old blind women who could see the future through an eyeball that they carried around with them. It was their job to watch the future and ensure that everything went according to plan.
(Quick sidebar: Eventually the fates came to share their job with the goddess Tyche, who represented luck and was believed to be responsible for the individual destines of cities. When the Romans came along, they rolled Tyche and the fates into a single deity, Fortuna (Fortune), who served as the goddess of both fate and luck. Finally, by the time you get to someone like Geoffrey Chaucer over a thousand years later, the goddess is simply called Fate.)
But we're getting sidetracked. The point is that when the Theogony opens, at the beginning of time, none of these deities have even been born. But wait: if there's no goddess of fate, then who's coming up with the prophecies? Exactly. The only person that we know who's directly involved with prophecy throughout the entire story is Gaia. So the big question: is it really Fate or is Gaia just manipulating things to turn out the way she wants?