Two banks around here merged together, and my Dad had an account with Bank A. When they merged someone at Bank B had an account with the same account number as my Dad. We were getting ready to move so there only a couple hundred dollars in my dads account, it just hadnt been closed yet. so my dad gets the bank statement for the month from them and they account had most of the money withdrawn, by the guy from bank B who probably thought it was his account.  Dad went to the bank and they fixed it and readily admitted they really screwed up. I've always wondered how they didnt think to see if any account numbers were the same across banks, and I wondered how many people that happened to.