The technology battering on Friday holds a lesson for high-valuation start-ups, one noted venture capitalist contended.

Chief executives of "unicorns," or private companies worth $1 billion or more, will start to learn what a price-to-earnings ratio is amid broad selling of tech stocks, Benchmark's Bill Gurley tweeted. The "cold reality," he added, is that ratios of 30 to 40 are "high."

U.S. stocks sold off broadly on Friday, with the Dow Jones industrial average (Dow Jones Global Indexes: .DJI) and S&P 500 (INDEX: .SPX) each losing more than 1 percent. The technology-heavy Nasdaq (NASDAQ: .IXIC), however, shed the most value of the major averages, falling 3.3 percent. Some of last year's most popular stocks took a beating, with Amazon (NASDAQ: AMZN), Netflix (NASDAQ: NFLX) and Facebook (NASDAQ: FB) falling more than 5 percent each.

Venture capital funding hit an all-time high of $128 billion in 2015 , as private firms like Uber jumped to lofty valuations. But rocky trading in recent months has led to more concerns about public market woes leaking into private funding.

Confidence among Bay Area venture capitalists rose in the fourth quarter of 2015 , but still lags the long-term trend, according to research released Thursday. The University of San Francisco survey indicated that the recent volatility could lead to an increased focus on fundamentals.

— CNBC's Anita Balakrishnan contributed to this report.

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