My friends have taken me to a game store, those ones with warhammer tables and magic card games... people don't wear deodorant there so he's got a bit of a point with the "gaming forum" line.
Side note on your argument, my friend has finally become a full fledged doctor (after 28 years!) and he's the smartest guy I know, but he's started typing like "Hey, how r u doin?" and it's simply because time is more valuable to him now so the faster he can get things out the faster he can get back to work. I agree with you though, I hate it and really emphasize using proper grammar with him but it's a lost battle.