Sorry to hear about all that. When you trade/sell you have to realize the ultimate risk you're taking. If this recent incident has upset you then you're actually making the right choice right now by quitting, or at least taking a long break or whatever.

I've been burnt in the past as well. Not scammed, but my personal invites were being resold and abused to the point of banning. What I've learned is that you have to keep your personal shit personal and your trading/selling shit separate unless you think you can trust the guy and feel like taking a chance.