Now there are signs of growing unease over the dizzying valuations of some of the most richly priced private companies.
The latest sign has emerged with one such favorite, Snapchat, being discounted 25 percent by one of its more recent investors, Fidelity, the mutual fund giant.
Another start-up, Dropbox, the widely used file storage service, was devalued by the giant asset manager BlackRock this year.
The funds’ markdowns may tap the brakes on a fast-growing market. Investors, in the hopes of getting a piece of the next Facebook or Google, have been pouring billions of dollars into young private companies."