Hormel foods has a position statement on the use of their trademarked term SPAM.

We do not object to use of this slang term to describe UCE, although we do object to the use of the word "spam" as a trademark and to the use of our product image in association with that term. Also, if the term is to be used, it should be used in all lower-case letters to distinguish it from our trademark SPAM, which should be used with all uppercase letters.

http://www.spam.com/ci/ci_in.htm