Pinterest Shares Drop on Weak Holiday-Quarter Sales Forecast (1)

Pinterest Inc. shares plunged the most in more than three years after the company issued a weak revenue forecast, a sign that the search platform’s advertising business may not be growing as quickly as expected despite the upcoming holiday shopping season.

The San Francisco-based company expects revenue to be $1.31 billion to $1.34 billion for the fourth quarter, according to a statement published Tuesday. The midpoint of that range is below the average analyst estimate of $1.34 billion, according to data compiled by Bloomberg. The shares tumbled as much as 21% after markets opened on Wednesday, their biggest intraday decline ...