Oh copyright, let me compare thee...
Okay, so Disney didn't seem too phased when purchasing Marvel last year that they could be facing some legal fights over the copyright pertaining to characters that Jack Kirby worked on for Marvel during 1958-1963. Kirby's heirs are now definitely fighting for his piece of royalty pie.
The big guys don't seem troubled by any of this at the moment. If you want to read the full story, and get confused over America's version of copyright laws, check out The New York Times link below.
The New York Times article on the lawsuits
Wiki entry on Jack Kirby
Marvel's Official site