I'm not allowed posters, except for one on my bedroom door. Since my wallpaper cost a fortune. But yeah, the one on my door is Good Charlotte, bought at my second of three gigs I've been to. :)
I've got over a hundred up on my walls. Not because I'm insanely obsessed and want to look at them everytime I'm in my room, but everytime one of my friends finds a picture of GC in a magazine they give it to me, and I always get at least 3 posters for my birthday, christmas, easter and valentines day.