A banner ad in a server list (ex- Bnet) or scoreboard ad (cs 1.6) is okay I guess, but I think what bothers me is the potential for an ad to feel out of place that it distracts from the immersion of the environment.
I'm a little uneasy about being in-game and then stumbling across an ad for a real product in the game world though I think it'd work just fine for a genre like sports.







