An additional argument against point (5) is that the number of shareholders doesn't matter, but the size of their holdings. A few shareholders at the top own the company, and then at the bottom there is a mass of small shareholders who, together, only own a small percentage of the shares of the company. So when it comes to making decisions, it's those shareholders with a chance of influencing who has a controlling interest that have the power to influence the company's management. And those few shareholders with large holdings can have idiosyncratic reasons for those holdings.  

Those whom the Gods wish to destroy They first make mad. -- Euripides