Ok, when I restored from an iCloud backup after installing beta 3 on Monday, my email accounts and everything else was there just fine. Last night, the phone managed to delete all four of my email accounts. Anyone know what might have caused this?
EDIT: I think it has something to do with iCloud. Last night, my phone tried to do an iCloud backup, but since my beta 2 backup used up 3.5 of the 5GB, it couldn't do the new backup until I deleted the old one (there's something about this in the release notes). I deleted my iCloud backup, and that seems to have logged me out of iCloud completely and also wiped my mail accounts, calendar, and notes from my phone.