Mivas: Unless they are actively trying to hack GOG servers, this step is completely unacceptable. Or are you suggesting that you want GOG to be more like Steam regarding service?
Not really. But still there could be some temporary restrictions applied to new arrivals, like a subforum accessible only after some time and at least one purchase. Even though there is a lot of hate towards Steam, it also doesn't lets you trade before making an actual purchase and having spent some time after.
I don't think we should borrow all the bad ideas, but there might be also some good ideas which are applied to other services.
Garran: That wouldn't help things much since new arrivals are apt to start posting on game-specific forums too.
It would probably be better to create a trading subforum with access restricted to people who've purchased whatever amount of games and leave the rest of the forum system alone.
This could also work of course. The most "light" idea i have is a separate trading rep. Which should have nothing to do with the forum rep. Just like ebay :D