The problem with online multiplayer gaming is the other players.
Internet enabled video games are, in my opinion, WAY more fun and have far more replayability than solo only games. This boosts the value of the game and makes the $49.95 price I paid for Project Gotham Racing 2 and Crimson Skies easier to swallow. Now, being who we are and what we are (competitive boys, but sometimes the ladies get into the mix), the online experience can be highly engaging, compelling and immersive. But this is a double edged sword because of who we are and what we are (again, boys).
Back in the day, online gaming meant gameplay with people you have never met and never heard. Now, with the Xbox communicator, I have to listen to anyone who wants to talk, and often it's a pure stream of epithets, abused english and stories about utterly random existential minutia. The game makers realize this and have started tossing up interstitial screens when logging onto Xbox live stating that the ESRB rating of the game make take a nose dive due to the real live humans out there.
Of course I can mute people, and often do so by going thru multiple menus (a slow and annoying process), or I can just take the headset off, but then I miss out on the benefits of voice communication in the game. Being able say "be at such and such a place on the far side and attack from the left" creates an incredible advantage against a disorganized enemy. Unfortunately, real cooperation is rare in the loosely organized games you find in public arenas, and most often the ESRB warning was right.