Paul Graham says he's unaware of many instances where company owners acted to screw small shareholders, and I believe he believes that, but I've seen multiple instances of exactly that†, and because my exposure to startup management is so much smaller than his, and because I don't believe the instances I'm aware of are correlated to each other, I think he's simply wrong about this.
†(most of those incidents started with the company encouraging departing employees to purchase their shares)
(This is probably a violation of their fiduciary duty to represent the shareholders, but who is going to sue?)