I'll add to the discussion about checks. I received a bank check for a lot of money. I took it to my bank (actually a credit union) to deposit it. They said the funds would be available in 5 days, but I questioned that and told them that I didn't know if the check was actually good. So i did not release the stuff until I got confirmation from my credit union 62 days later that they had received the funds. (And I checked in with them every week!)
I've also sent an overseas wire transfer to the address the seller gave me. I got confirmation it was sent, the seller never received it. I was able to have the wire transfer undone (minus 2 wire transfer fees).