I’d like to dismiss this as a hoax, but there don’t seem to be any of the telltale signs of a hoax, such as sarcastic recipes for “mooseburgers & cheese” or reminders to force-feed wayward daughters Depo-Provera. 
Anonymous is the hacker group allegedly involved – they surfaced a coupla few months ago, issuing some quasi-juvenile, supposed-to-be ominous threat against Scientology. Apparently, they’ve taken time off from harshing the Operational Thetan Level III’s volcano buzz to turn their attentions to the Republican VP nominee/snowbilly queen, Sarah Palin.
Here’s what Gawker had to say:
Did the internet just cause Sarah Palin
to destroy evidence? The potential Veep is in a bit of trouble for
conducting state business using her personal, unarchived email address
(gov.sarah@yahoo.com) instead of her official account (which is, of course, subject to laws requiring the retention of government records). Emails from that Yahoo account are already being sought in connection with the Troopergate investigation. Now comes word that Anonymous, the fun-loving Internet trouble-makers based loosely around the message board 4Chan,
gained access to another Palin email account: gov.palin@yahoo.com. It
looks legit! The offending posts, screenshots, heretofore unseen family
photos, and emails have all been deleted from Imageshack and 4Chan. But
we have them. You want to read Sarah Palin’s email?