Originally Posted by Oracle

Second, they don't want to cross-platform because they want to protect their console from the exposure of the overwhelming amount of pandering they provide it. Microsoft tested cross-platform games (actually, just one) upon the release of the 360 with Shadowrun, a fps that was quickly forgotten about because nobody on console or pc wanted to play it. However, when they beta tested it, they decided to try to prove "console superiority" by recruiting the best console players they could get, "professional" players, and pairing them off against, literally, players they pulled off the street for PC, to "prove" that console players were better.

The result? The random PC players crushed the "pros" every game. Microsoft hushed this up as best they could, but it got leaked to a couple sites several months later. Every since then, Microsoft has not bothered to implement cross-platform play into ANY of their games. They can't sell a product to one market if it gets proven that you will get annihilated regardless of how good you are by somebody who purchases an identical product for a different market. And the FPS genre pretty much dominates the console market right now. Implementation of cross-platform play would pretty much decimate these sales, in theory.