So you decide to sell your old motorcycle on Craigslist after you but that new Harley! Great idea, the ad price is right (free). You take a great picture and include a perfect description and a fair price. The first day listed, you receive a call from someone calling from out of state. They want to buy your bike, they will send a money order for the total and also some for shipping it to them. This is going great the bike will be sold in a couple days.
When you receive the money order, it is for three thousand dollars more than you had agreed to. Being the honest person that you are, you call the buyer and explain about the extra money. the buyer tells you not to worry, they were doing a few transactions and got a couple of them confused. They tell you to go ahead and deposit the full amount into your account and wire them the difference so they can get it to their other seller right away.
No problem you say, what could be wrong with this scenario? It is possible for a money order to initially clear your bank and then "bounce" a few days later. Now, not only do you not have the money for your bike, you are also out $3000 that you wired to the buyer. Since wire transfers are immediate they can't be undone days later. Hopefully you didn't already ship out your bike to the buyer. If you did you are also out that also. The best policy is to deal locally.
This actually happened a few years ago to a person in Denver.