Seems like you should be pretty okay. Something Awful does something like that as well, and I've never heard of any serious legal problems. At worst, they'd send you a cease and desist and you could just mock that (read the story about drugs on 27b/6!)
I don't really use Amazon that much to justify a prime account. I think if I got one, I would start using it more, and I'm sure that's exactly what they want me to do lol.
edit: exactly like 007 said two posts above lol.