I was talking to a friend who has his aircraft titled through a corporation and he said something that made me think that I was previously not 100% correct, so I looked it up. Either the rules have changed slightly or my memory is defective, err, slightly
Here is the official answer:
The basic requirements for documentation are to demonstrate ownership of the vessel, U.S. citizenship, and eligibility for the endorsement sought. .....
....In addition to individuals, corporations, partnerships, and other entities capable of holding legal title may be deemed citizens for documentation purposes. Corporations must be registered in a state or the U.S; the chief executive officer and chairman of the board of directors must be U.S. citizens, and no more than a minority of the number of directors necessary to constitute a quorum may be non-citizens. In addition, at least 75% of the stock must be vested in U.S. citizens for a coastwise or fisheries endorsement.