VC returns are not what you think they are. There is a lot of dumb money floating around and the long term returns of quite a few funds are much lower than what you might think. A couple of funds outperform the remainder quite handily which results in an average that looks acceptable but quite a few people lost a lot of $ on becoming an LP of a badly managed fund.

That won't stop the fund managers from making out like bandits, the carry may be nil but the management fees will more than make up for that. Beware of investing in funds where the fund managers do not have substantial skin in the game.