Does it seem strange that a bunch of the people who rated this shirt on July 28 also registered with Threadless on July 28 and have only rated one shirt, giving it a 5?

Not that there's anything wrong with that. I just wonder if this is normal. Is it worth it to have a bunch of people register for one shirt?
http://www.threadless.com/submission/48551/she's_in_love_with_what's_dead