Google Inc.’s stock price fell by more than 4 percent Monday, accelerating a recent shift in sentiment that has caused once-ebullient investors to become more circumspect about the online search engine leader.

Barron’s cast the latest pall on Google with an article outlining several risks that threaten to squeeze the company’s profit margins and cut its market value in half.

The gloomy scenario further dampened investors’ enthusiasm for Google, whose market value has plunged by 27 percent during the past month to wipe out nearly $40 billion in shareholder wealth. Google’s shares fell $16.91, or 4.7 percent, to close at $345.70 on the Nasdaq Stock Market.