There are also instances though where the FDIC can't find another bank willing to acquire the failed institution, so it can't just close on a Friday and then reopen on Monday as a branch of a new bank.
One of those happened just last week:
http://www.fdic.gov/bank/individual/failed/commbank-ct.html
So it seems like in an instance like this, while you get a check for your insured deposits from the FDIC, your bank is gone and presumably any auto-debits or outstanding checks would fail to clear. You get to wait for the FDIC to mail you a check. Then you'd have to find yourself a new bank. This seems like something that would be fairly disruptive even if you are not poor.