The FCC has some power in that regards, but it's only applicable in regards to broadcasts (since the airwaves are considered public property). Internet and cable are becoming much more important, and the FCC can't step in there without violating the first ammendment. But while there's this worry about "big media cooperations", the fact is we've got a more diverse media than we've ever had before.
Oh, and nothing about antitrust law (which is what it's called) prohibits comapanies from becoming monopolies. All it does (and all it should do) is restrict it's ability to create barriers to entry for any new competitors which might emerge.
That's a nightmare. What constitutes a "misuse"? Who gets to decide what is a misuse, and what powers will they have to punish such misuses? Why would any media organization with contrarian viewpoints ever allow itself to be punished by such a panel? And how the hell do you prevent the panel from devolving into enforcement of whatever ideological party line manages to gain control of the panel? I actually know the answer to the last question: you can't keep it from happening, you can only hope it doesn't. Which isn't good enough.