Grellas wrote a very informative series of "Startup Law 101" posts. Well worth reading:

http://www.grellas.com/faq_business_startup.html

All these questions I plan to answer in this blog. Personally, I couldn’t find a blog like you had described and that is why i decided to focus on these topics in our own blog.

What sort of mistakes did Zuckerberg make?

when investor become a shareholder of the company, the shares were derived from Eduardo Saverin (co-founder) shares only