When this guy dies, his legacy will be to have been at the center of a fundamental shift in the consumer landscape, one which consumers have jumped on board with wholeheartedly because they really like the service he is offering. Just to be clear, he is rich because so many people loved what he was doing that they decided, of their own free will, to use his product extensively. While I think we should be sensitive to making sure he doesn't become a veritable Scrooge McDuck and things don't only flow up, I have a bit of trouble getting outraged over how rich he is when I choose to make him more rich, willingly, with some frequency, and I get something out of it that I place significant value on. I suspect the same will be true for a lot of people who will be outraged in this thread.
Beside that, this is all beside money he does put into developing technology and infrastructure. Again, when he dies, he will have changed the world, and arguably for the better if we judge "the better" by a standard of "providing more things that more people want."