I was under the impression Zuckerberg was never paid. There was never an agreement of payment and no one signed anything. If I'm wrong, so be it, but if someone came to me with another "Make us rich" idea and all I had to do was implement the entire site for free and they would graciously give me a cut of the profits they can kindly suck an egg.
It happens all the time to me and I'm sure to you as well. Someone suggested I implement an iphone app that scrapes the exchange web interface and gives you calendaring, email and all the other goodies because he was stuck logging into a locked down server blah blah blah. All I had to do was code it all up in a weekend and he'd split the money with me.
So lets say I actually looked at the feasibility of it. Now if I go off and implement a revolutionary email program for android and make a billion dollars do I owe him anything?