Who is feeding the unicorns?

I read a great article in the WSJ tonight about who is feeding the unicorns (investing in private companies at high valuations) and more importantly why -- "Mutual Funds Flail at Valuing Hot Startups Like Uber."

Mutual funds have been aggressively investing in these private companies.

Why?  First the greed: "getting in early gives those mutual funds a shot at a huge profit if a company takes off, which happened with Facebook and LinkedIn."  Second the fear:  "Many of those managers also are struggling to compete with lower-cost mutual funds that track a market index."

Size?  "At some funds, private companies are one of the biggest single investments." For example, Harford Growth Opportunities Fund (one of the best-known mutual-fund investors in startups) had 1.7% of its $4.7 billion fund in Uber, while 3.5% was in Apple.

Concern in a Downturn?  "In 2004, Van Wagoner Funds, a large investor in privately held startups during the tech-stock boom of the 1990's, settled civil charges in which the SEC alleged that the firm misled shareholders about the size and value of the funds' investments in illiquid securities....  An SEC spokesman declined to comment on whether agency officials have any concerns about the valuation procedures now used by mutual funds."  Will this WSJ article raise similar concerns, especially with negative articles on Silicon Valley sentiment (such as Dan Primack's Fear and Sadness in Silicon Valley).