I had the same issue yesterday all my exchange accounts are gone. I had very good feeling about so called "DROID", but no more. I am going to iPhone or may be Windows.
My Droid OS version is 2.2.1, still it keeps dropping exchange accounts.
My next phone was Droid-X but no more. Such a big bug, cann't believe.
I was losing the Exchange email account from Original Droid on Verizon every two weeks or so, while all other accounts stay intact. Lost it three times in the last two days, so it is getting to be a REAL problem...since you don't know it is gone until you go looking for it, or wonder why there are no new emails. I know this problem has been reported for years...any new information anyone?