Hormel, makers of SPAM, is suing SPAM ARREST, purveyors of spam-blocking software, according to this Seattle Times article. 

Here is the text of Hormel v. Henson, wherein Hormel could not stop Henson from using Spa’am as a name for a wild boar in a Muppets movie.  Here are the spam haiku archives.  Here is the Monty Python spam sketch.

And it is interesting to note that Spam Arrest owns a federal trademark registration for SPAM ARREST (disclaiming SPAM).