Thanks so much for posting about this. I'm learning more as I see what people are saying about this/reacting to it, so I really appreciate that OTW has made this post.
I would LOVE to get in contact with your laywers and/or share the back-and-forth Zazzle emails with OTW. I requested a DMCA notice, but Zazzle just told me the removal of the products was part of a 'routine sweep from Viacom'. Recently, another NEW product was removed by Viacom claiming that I had 'copyright infringement on intellectual property'...which led me to believe that they are searching for any sort of image names or keywords that have the words 'airbender', 'viacom' or any of the character's names. I changed the name of the image (to V1acom instead of viacom) and put the product back up; I'm now curious to too if it'll be removed as well. :D
Also, I'm a little intrigued at what Michael Fricklas has said in the comment above.
But overall, I really want to talk and learn more about what I could and should do. I've been advised to file a counter-request for the DMCA notice from Zazzle...could I contact you regarding this process?