Left 4 Dead 2 on Xbox Live with your friends, well, we think you're a bit strange and should likely find a better habit. That being said, you'll be happy to hear that the game will be free-to-play for all Xbox Live members (even you lower class Silver folks) next weekend, starting promptly at 12:00PM ET on Friday, January 15, and finishing up on Monday the 18th (also at noon, as confirmed to CVG by Microsoft). We can't imagine that those of you still holding out will be convinced of an Xbox Live Gold account's worth after just one weekend, but it certainly can't hurt, now can it?
Update: The free weekend has been confirmed for Europe only. A Microsoft representative tells Joystiq the company has "nothing to announce at this time" about a North American promotion. When asked if they had a timetable to announce something, the representative politely said that we'll hear something soon one way or another.