If the problem is as pervasive as the devs portray it, these sites will quickly cease to exist--G2A would quickly gain a reputation for selling keys that will be useless after 2-4 weeks, and the benefit of getting the game for cheaper would be outweighed by the risk of the key going bad.

That doesn't seem to be happening though. I don't buy the argument that a huge number of G2A customers simply never notice that they've lost access to the game (not to mention what that implies about the quality of your game).

I'd never heard of G2A before this, but I'll be checking them out the next time I'm considering buying a game.