Facebook's stock price isn't the only thing that's dropping: The year-over-year US user growth rate has taken a dive, too, reports the Wall Street Journal. April saw 158 million US unique visitors, a boost of 5% from a year earlier, according to comScore. But that 5% is a fairly paltry number, considering Facebook saw 24% growth in April 2011 and 89% the year before that. And while the time users spend on Facebook is still growing—up 16% from last year to more than six hours per month—that rate is slowing, too, down from 23% last year and 57% in 2010.
But the Journal tempers the news with the admission that the slowdown isn't actually too surprising, considering how much room Facebook actually has to grow here. It already lays claim to 71% of all US Internet users, and that six hours a month is significantly more than the four hours they spend on all Google sites (including YouTube). But critics point out that Facebook's IPO sales pitch emphasized the company's double-digit growth rates, and with 56% of Facebook's 2011 ad revenues coming from the United States, slowing US growth hampers its ability to grow revenues. (Read more comScore stories.)