I would also add on to the context of Tesla and SpaceX. Now part of this is speculation on my part. But I would also like to propose that the problem domains of

I would also add on to the context of Tesla and SpaceX. Now part of this is speculation on my part. But I would also like to propose that the problem domains of Tesla and SpaceX also attract people who have vested interest in the problem domain. Engineers and researches at both of those companies are passionate about the problems that those two companies are trying to solve. With Twitter and social media, maybe there exists some people who are passionate, but I imagine the biggest attraction of Facebook and Twitter are the pay and the resume item. But at Tesla or SpaceX, your willing to eat more shit because your working on something your probably really passionate about and not to mention badass. I don't like Musk, but I would worked for him at SpaceX just because rockets are badass and I like space.