Newly Public Tech Firms Face Reality 

(Bloomberg) -- Wall Street is tapping the brakes on newly public technology companies after a runup in their shares.

Carbon Black Inc., which held an initial public offering in May, hit a record low as shares tumbled as much as 8.1 percent intraday. Other companies that have done IPOs in the past year are also feeling the sting, including Zscaler Inc., Zuora Inc. and MongoDB Inc.

For MongoDB the "current market reflects extreme valuation," writes Nomura Instinet analyst Christopher Eberle in a note to clients, downgrading the stock to reduce from neutral.

Collectively, these four tech firms have wiped out almost half a billion dollars from the market as of midday in New York.

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