Google (GOOG) is finally discovering gravity. First, the company missed Wall Street revenue forecasts in the fourth quarter for the first time. Then a pair of reports from market researcher comScore (SCOR) , the latest on Mar. 26, said US. growth in the number of clicks on the paid ads appearing next to Google's search results essentially flatlined for two months running compared with a year ago. Six months ago, paid clicks were growing up to 40% annually.

The combined news was enough to send sentiment about Google crashing to earth. Its stock price has plunged 38% from its all-time peak, an intraday high of $747.24 last November, one of the worst performances by a blue-chip tech stock. The big worry: A tanking economy could ground the company's unparalleled rocket ride. "The whole Street has turned cautious," says American Technology Research analyst Rob Sanderson, who notes that 16 analysts out of about three dozen have cut Google's first-quarter profit estimates. "Everyone's scared."