IANAL, however what the majority of shares vote for is not the same as what is in the best interest of shareholders.

For instance, Zuckerberg controls Facebook. He can not decide to use all Facebook's cash as his own personal bonus. That is because it's a clear violation of his fiduciary responsibilities to minority shareholders.

Minority shareholders have a right not to be screwed, though it is VERY difficult to establish misconduct in private companies.