It is all fine and good to say he is a hard guy to get hold of but I believe if you are going to take peoples money, you owe them a responsibility to get their goods to them in a timely manner, and if you can't for some reason the polite thing to do is to at least make contact with them.
You don't want negative stuff about you all over the forum. That just makes it harder for you to sell anything on the forum the next time.
If people commit to you and send you their hard earned money, send their stuff. It's the principle nothing personal.