Don't you think that their association with YC would protect them to some extent from trickery like this? After all, the collaboration with YC is widely published and it would get significant press as well as close a bunch of doors if he did something like that I would imagine?
All the other 'zucks' notwithstanding there has yet to be a clear cut case of fraud to come out of all this and I can't imagine YC et al would stand by idly if this happened to one of their investments.
Zuckerberg's moral compass is set on "WIN."