For what it's worth, I have dealt with Dave before and there wasn't any problem.
As I see it, Dave's only mistake was putting himself in the middle of a deal for a friend who he was trying to help out. Based upon the story I read, here, it sounds like the friend was responsible for the delay - not Dave. And Dave got blamed.
Morale to the story is not; Don't do business with Dave.
Rather it's don't get involved in selling a part for a friend (even a $25 one) unless you have a key to his garage - and he lives in the same state....
As for the buyer, go buy the same mirror on EBay for 4 times more than what you paid here and be happy he refunded your money. Sometimes getting a great deal on something means putting up with some hassles - like waiting an extra month or two. Dave sent your money back which is way more than any rip off artist would have done.
If you hang around the Porsche used parts boards long enough, the law of averages will eventually prevail, and you will eventually be boned for a lot more money than this. Take a look at some of the threads of people who have REALLY been ripped off, and then appreciate the fact that you are not one of them.