The Oscars are about awarding people whose "time" is due. Kathryn Bigelow didn't even get a Best Director nomination this year (though she deserved it) because she'd already "got hers" with The Hurt Locker. Ben Affleck also missed out because the Academy still remembers when he was one half of Bennifer, and he'll need to do a lot of "serious" work to redeem himself after that. I know someone who voted for the SAG Awards (pretty much the intra-industry lead-up to the Oscars), and it basically goes based on personal preference.
Did you see the article I posted in the run-up to the Oscars where an Academy voter shared his voting process with a journalist? It was really interesting stuff.