Steve O’Donnell, over at 3C Patent Law, has a nice, quick description of how a trademark owner can lose its rights through dilution. I’ve excerpted some of it here, but read the whole post for a better explanation:
Consider this hypothetical: Chick-Fil-A does nothing about “Eat More Produce” because its considered too far-fetched of a claim to make; later, someone starts using “Eat More Seafood” and Chick-Fil-A does nothing because they don’t sell seafood; later someone starts using “Eat Mor Tofu,” that’s getting closer, the misspelled “More” is making this a pretty obvious trademark issue. Let’s go one farther and say that some eventually starts using “Eat Mor Turkey.” That finally gets Chick-Fil-A’s feathers ruffled so they take it to court. The judge looks at how Chick-Fil-A has allowed others to use similar slogans without doing anything to police their mark and quite possibly rules that Chick-Fil-A has lost their trademark because they haven’t done anything to protect it.
Looks like Chik-Fil-A is just doing what Hansen did to protect its trademark MONSTER.