I'd confidently state that I love capitalism, but I'm not very happy with the idea that Uber could turn 17 billion dollars into 7 billion dollars and then hand the bag to retail investors.
The thing I tell myself is that the money is all going to the same place anyway. Yeah, Uber is going to cash out and bomb from their IPO price, and everyone who buys will lose. But anyone who would buy Uber is going to do any number of equally irrational things with their money, not to mention the fact that no matter who "owns" the money it will either be sitting in a bank or another asset, so it doesn't really matter.