The a16z deck posted a couple of days ago made a great point relating to this. In the past, an IPO would allow everyone to participate in the upside (e.g., 1000%+ growth of the Microsofts and Oracles). Now, the ones reaping the rewards are the private equity groups. By the time they unload companies on the public markets, most of the upside is gone.

https://a16z.com/2015/06/15/u-s-tech-funding-whats-going-on/