In the last ten years, probably 25 or so (buying), and almost the same number selling.
GunBroker, Guns America, and Auction Arms, several each. THR, TFL, and S&W Forum, at least several each. Texas CHL Forum, more than that.
I can honestly say that I have had exactly one negative experience. Guy sold me a Charles Daly 1911 that he said worked perfectly. It did, for one round. Jammed almost every other round. I asked him about it and he denied ever having a problem with it. Later, found that he had made a number of posts on different forums using the same user id (Darkness) repeatedly calling the CD 1911 a "jammomatic".
Here's one: Posted on the S&W Forum 08 March 2006 08:45 AM
"I carry Black Talons in my Charles Daly Jam-Master 2000 compact."
He's a member on THR, too, although he doesn't appear to be hanging out here recently: Here he's asking for help with said 1911.
http://www.thehighroad.org/showthread.php?t=183108
Guess that instead of fixing it, he sold it to me.
His name is Tony Vanelli, and he lives in Cincinnati. Avoid him.