I wonder if people ever read the legal stuff in sponsored challenges
"For all Designs submitted for use by Threadless.com, you acknowledge that the Design is considered a work-for-hire as defined under the United States Copyright Act of 1976 and will become the sole property of Viacom Media Networks and its subsidiaries and affiliates (hereinafter collectively "VMN"). To the extent that the Design may not, by operation of law, be a work made for hire in accordance with the Design Submission Terms and Conditions, you agree to assign to VMN the entire right, title, and interest in and to the copyright in your Design including the right to sue for past infringement and the right to further sublicense the Design. You also acknowledge that you waive all "moral" rights that you may have in and to your Design."
Just so you know.