1) What if your company is indeed growing but not scaling at the rate that it needs? An investment would boost that ability correct? An owner would be able to hire more employees, perhaps buy more necessary technology, etc.

2) I don't think that is good advice. Zuckerberg had built things previous to Facebook but never anything that made money. I am not as familiar with Twitter and Pinterest's founders but I don't believe they had money-making businesses before. If a service is good and attracts people, why not build it??