How easy it is to recover a post, seems to depend on the browser you're using. My lame old Netscape used to lose posts all the time. The Firefox versions I've been using lately (2, 3, and now 9) are so good at saving stuff that I've been able to get back to a post I was working on even after an hour-long power outage.

If I back up to the page where my post used to be and there's just a blank text-editing box, clicking Undo or Edit > Undo will often bring it back.