Here's another great examination of the difference between trademark and copyright, courtesy of the great Stan Lee.
Stan Lee's current company, Pow! Entertainment, was recently granted a trademark on the service mark "Excelsior!"
Excelsior, besides being Lee's catch phrase, is also the name of the book he did awhile back...
In the pages of Runaways awhile back, Brian K. Vaughan introduced a team of young superheroes that formed a sort of superhero support group. They called themselves Excelsior.
That was fine, because Marvel was not using the name Excelsior in any advertisements or as the title of the book - basically, there were not using the mark in commerce.
However, in late 2006/early 2007, they announced plans for a mini-series featuring Excelsior.
Here, there would be a problem, because they would have to use the name in the title of the comic, and by doing so, they WOULD be using the mark in commerce, which is where they would come into conflict with Lee's trademark.
So they renamed the book Loners!
Interestingly enough, Lee's trademark was only recently granted by the government. I wonder when his company actually filed for the trademark. This might very well have been a case of Marvel backing off before any legal problem actually occurred, perhaps because, well, why mess with Stan Lee if you don't have to?
If anyone knows of any specifics to the situation, let me know! I know Rich Johnston mentioned it, but that was source-less (which is totally fair, just noting that if anyone had a source, that'd be neat).