Those performances have also driven the market for initial public offerings to heights untouched in the United States since the boom year of 2000, according to data from Renaissance Capital. Internet and biotechnology start-ups have rushed to claim public listings, especially given some rich performances by notable debutantes. FireEye, a noted cyber security firm, had at its height nearly quintupled its I.P.O. price of $20 a share since going public last September.
But momentum stocks rely on investor exuberance to continue their growth. And as that enthusiasm evaporated, so too did those once-magical gains. FireEye slid 8 percent on Friday; Illumina fell nearly 6.7 percent.
NXP Semiconductor, whose 35 percent rise from Jan. 1 through Thursday made it one of the best performers in the Nasdaq, tumbled 7.4 percent.
Few analysts agree on what spurred the sell-off, though Mr. Leone hypothesized that biotech companies suffered from pressure on the prices of their products,especially after Congress asked one drug maker, Gilead, how it could justify the $84,000 cost of its hepatitis C treatment Solvadi.
Not all was doom and gloom, even on Friday. GrubHub, the online food delivery company beloved by financial industry employees, survived a wild ride to close 31 percent over its offering price, at $34 a share. IMS Health, a major seller of prescription drug data, closed up 15 percent over its I.P.O., at $23.
And less-supercharged technology stocks suffered far less. Shares in Intel, for instance, ended Friday down just under 1 percent. Those in Oracle fell even less, closing down about 0.7 percent.
Analysts are of two minds over what will happen next. Some believe that if investors continue to flee these momentum stocks en masse, the damage could bleed over into seemingly unconnected companies. Mr. Leone of Macquarie said that because many of these growth companies are widely held in various indexes and exchange-traded funds, a continued plummet could hurt others in those bundles.
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He says he remains skeptical that investors have finished their selling.
"It's hard to say that we're really done," he said. "There's no valuation support for these stocks right now."
One potential area that could be affected is the I.P.O. market, if the venture capitalists and private equity financiers who back many of the start-ups worry that they cannot get the sky-high valuations that had become the norm. Kathleen S. Smith, a principal at Renaissance Capital, noted last week that investors had been pushing back against pricing in some new stock issuances.
Nowhere was that more evident than with King Digital, the maker of the wildly popular Candy Crush Saga. The game maker priced its offering in the middle of March at $22.50, in the middle of its expected range, only to see the stock price sink below that almost immediately. King's shares fell again on Friday, sliding nearly 5 percent to $18.96.
But others cautioned against expecting broader damage to the market. Momentum stocks could continue to gyrate for some time, but the broader market should remain relatively unaffected, said Matthew L. Rubin, the director of investment strategy at Neuberger Berman. In fact, investors have already shown a flight to safer havens in value stocks.
Moreover, some of the sell-off could be tied to benign reasons, including investors wanting to cash in gains ahead of tax season.
"I think this was isolated in the momentum stock arena," Mr. Rubin said. "A pullback was sort of in order."