I used to get guys like this all the time when I was selling parts. I would leave them hanging for months with different excuses why I couldn't "forward their payment to their shipping company" an email here and an email there and eventually I'd tell them that I spent it gambling or on crack, or sent them a check in the mail. Most of the time they stop communication, but sometimes a feisty one would come along with threats and pretend they're the FBI, etc. etc. Good thing I always used a fake address.