[ineedasername]

On stepping down or being forced out: Regardless of any other factor, it's because he controls roughly 60% of the voting stock. He has about 18% of the stock, but his class-B shares get 10 votes per share, while normal class-A shares get only 1 vote. So it would take something truly black-swan level to get him out.

[ineedasername]

What exacerbates this even more is the fact that once sold, Class B shares lose their privileged status and become class A shares. So as employees with B shared gradually leave Facebook for other opportunities, Zuck gains even more power relative to the rest of the voting stock.