Tedd Richardson has a good post about fraud:
Just because someone at the bank tells you a check is good, it might not be the case. Here is a story written by Caroline Mayer of the Washington Post, where someone selling a car on a auction site received a check for more than the amount of the purchase and was asked to wire the excess funds back. The seller was suspicious and asked a teller at his bank (twice) to verify the check and was told it was good. Here is what happened next as Caroline Mayer reports: "Four days later, as he reviewed his account online, he discovered the check was not good. Even worse, the bank was demanding that he repay the $5,000."