It’s enough to put you off Avengers, Superman and …. well most of them! … almost.
According to Sci Fi News:
Marvel and DC sue small publisher over using the word superhero
http://www.blastr.com/2013-2-1/marvel-and-dc-sue-small-publisher-over-using-word-superhero
Recently an indie publishing house found out the hard way that Marvel and DC share a surprising trademark. Cup O Java Studios’ title A World Without Superheroes recently got slapped with a cease-and-desist from both Marvel and DC. Why? It turns out they jointly own the trademark to the term superhero. In fact, they apparently own the right to every permutation of the word, regardless of spelling.