There is something apt about a social networking website winning a popularity contest. According to industry data, Facebook overtook Google among US internet users last week, with more visits to its pages than to the search engine. It is a moment to consider the rapid growth of a site whose 400m-plus users outnumber the population of any single country except India and China.

The industry data come with a few caveats. The figures exclude visits to other Google services, such as YouTube and Google Mail. They omit searches carried out in a box on a browser toolbar. Also, the number of visits is just one measure of internet take-up: counting unique users – visitors rather than visits – gives a different profile. Still, it highlights the momentum behind Facebook as it displaces Google.com from the weekly lead it has commanded on this measure since September 2007.

Advertisers find Facebook appealing too. It enables them to reach a mass audience, as television does, but with the extra benefit of much greater targeting. Consumer brands could easily extend their presence beyond the fan pages that already exist. Moreover, a social site provides consumers who visit for much longer than they would use a search engine. So increased advertising, and perhaps ways to allow users to shop through the site, should enable Facebook to move from positive cash flow to making profits.