For me it's the next evolution of playing with my figures. It's fun to see how creative others can be with their collections or imaginations. It also means I take a LOT of hell from friends and family when they hear about this hobby . I lurked around for a bit, then joined up after I finished Grad School. I don't post as often as I'd like due to "real life", but I check in every day to see what others have done.
I've been around for a few years now, and have seen some of the drama that has come and gone. I've done my level best to stay out of it, but I'm sure some have complained about me from time to time.
I just want to say we seem to be getting lots of new talent daily, and that's great and encouraging for this hobby. I'm on several groups on flickr as well.
By the way, my hometown baseball team (And Duke's and Spearhead's by the way. Check out their file cards.), the St.Louis Cardinals, had just won the World Series when I finally signed up. Thus the goofy-sounding name "GoCards".