When I went to Six Flags over spring break I saw a ton of kids wearing these shirts. 7-Up is very smart .. By appealing to the kids' sense of rebeliousness, while not being too extreme ("Mom, it's just a slogan for a drink!"), 7-Up has created the ultimate in advertising: Walking billboards that pay YOU to advertise for you.

Think of it as an integrated advertising scheme. The shirts fit in with the commericals.