I was impressed to see how little venture capital SpaceX has taken over the years. Of course there was a lot of funding from Musk (is this the seed funding in '06?), but very impressed to see them build out very successful and complicated products with only a few hundred million before 2015. Looks like they are now confident enough in their process and goals to begin accepting lot's of venture capital.

It also seems to me that SpaceX should not be in this list. Being a company that focuses on physical technologies, it is almost a different beast altogether than the rest of the software-based group. Hard to compare it's company and funding structure to the others when it involves a much more complicated logistical chain, development period, and roll out.

EDIT: SpaceX has received almost $1 billion in funding from NASA over the years. It's unclear to me, however, how this funding works. Is it an up-front payment for future launches, or purely award money?