Yep. The symbol for pi is a trademark as of a few months ago. Some dickwad artist decided he'd trademark this:
He's now been sending cease and desist letters to all sorts of companies selling t-shirts and such with the pi symbol on it.
I had to check the date to make sure it wasn't April Fool's, but sure enough here's the trademark:
http://tmsearch.uspto.gov/bin/showfield?f=doc&state=4808:39iukm.3.2