Learning to be an investor

I've been an entrepreneur since 1994 -- that's almost 14 years.  I'm surprised at some of the basic lessons that I'm learning as I become self educated as a seed stage investor.  Having started and run 5 companies over the past 15 years gives me lots of insight into the management of the companies that are pitching me on investment. Currently, I'm trying to figure out how exactly to apply my experience -- which is still relatively unique in the investment community -- to investing. 
The question I'm asking myself today is -- would I have invested in Twitter early on.  My answer is -- I think not.  I would have understood the entrepreneurs and gravitated toward them, and I would have understood thee messaging platform, but I would  have likely dinged the business because of its lack of a revenue engine.  This is all mute -- because I never invested nor was I asked to invest but it's all part of evolving my investment perspective.