"Piketty converts the entrepreneur into the rentier. To the extent capital reaps high returns, it is by assuming risk (over the broad sweep of history real rates on T-Bills are hardly impressive)."

The high returns entrepreneurs and investors can receive is a result of capturing winner-take-all market opportunities. Mark Zuckerberg, for instance, took very little risk in the scheme of things. I heard a talk by a Sequoia partner once. He said that their investing philosophy is pretty simple: Look for billion dollar market opportunities, and invest in the team/company most likely to capture that market. Thanks to Sequoias's reputation and contacts, they can attract the top entrepreneurs and thus earn extraordinary returns. Risk has little to do with it.

Much of the risk in startups actually comes from the fact that the market opportunities are usually pretty obvious, so there are a bunch of startups competing for the space, and only one or two can win. There are some entrepreneurs who take on genuine technology or market-existence risk, but this tends to be the exception these days.