This kind of thing won't happen to Steam, at least not this way. The critical difference is that when you make a match, Xbox Live or an affiliate company gets to host the game, so in their view, the original Xbox oldies are taking up bandwidth and server resoures that could better be used to host X360 games. Steam, on the other hand, is merely an interface. Games are hosted by the end user, not Steam, so there's no incremental cost to them. You simply can't do that with a console though, because most console gamers out there don't even know how the non-centralized setup works, or that it even exists.