I've bought 1 before, was a HUGE player lot, mostly commons, inserts, and rookies, of top players, Kobe, Barkley, Iverson, T-Mac, Duncan, Shaq, etc etc etc. Basically I told the seller who I was interested in, and they sold me the cards.
They had 2 T-Mac GU cards advertising in their auctions, and I got both.
I had a good experience at the time (wouldnt waste my time/moeny now, with my goals for collecting).
The ones you see advertising all the "MJ Rookies, Bron Autos" etc etc etc, ARE SCAMS!!! Pure and simple.
But the one I got, he was honest.
Just see what you are buying into if you decide to buy one...