[sgdesign]

Yes, this definitely seems like a mistake on Zazzle's part.

And it's possible the artist may have been acting in good faith, and only wanted designs that actually copy his brand removed, not all designs featuring pi.

Edit: OK, it does seems like the artist is also abusing the system here, judging by his other trademark: http://news.artnet.com/art-world/artist-who-trademarked-pi-s...