I have a relevant, but totally anecdotal observation to add to this, Dean. I noticed it immediately upon picking up the Xbox 360 on launch day and logging on to Xbox live. Perhaps it was the pure joy of unleashing the power of a new system, or some kind of honeymoon period of Xbox Live Love, but whatever the cause, the effect was a kind of eerie calm. Players were actually nice to each other. Common practice in Project Gotham Racing was to warn your opponents if you were pulling out of a draft maneuver to pass them or (gasp) even apologize if you bumped their car into a spin on the way by. On two occasions I even got into real conversations with other players I'd never met before.
When did this strange calm period end? When did Project Gotham players start slamming you into a wall and cursing your mother on the way by? Why December 25th of course, when hundreds of thousands of pounds of teenagers ripped the wrappings off their shiny new 360's and joined the fray. Perhaps the solution is as simple as requiring a mandatory verified birthday entry somewhere in the signup process, and allowing players the option to filter out their matchmaking by age. I know I yearn for those days of the 360 launch when, "hey, passing on your left, man" was much more common than, "bleep your bleeping mom on the wall bleep!"
Jake
TheGameChair.com