I've been a lifelong Ohio State football fan - I never cared much for any other collegiate sport. I was lucky to go to THE school that I had always rooted for for my undergrad. I went to grad school at Kentucky though, and got in to the basketball culture there. It really is something else - along the lines of the fanaticism you see around the Shoe every Saturday in the Fall.
I don't really consider it bandwagon but some do.