Last week more people in the US visited Facebook than they did Google according to Hitwise.
The social networking site had previously hit the top spot on individual days, including Christmas Day and all of them major holidays, but this is the first time it has outstripped the search engine over the course of a week.
Moreover, days on which the site has been the most visited in the US have been seen more often since the turn of the year.
In the week ending March 13th, 7.07 per cent of all US internet visits were to Facebook, compared with 7.03 per cent over the same period for Google.
Perhaps more tellingly, a comparison to the same week last year shows that Google's market share increased by nine per cent, but Facebook's share of US internet traffic rose a massive 185 per cent.
Facebook now has more than 400 million subscribers and, it has been widely reported, is on track to generate more than $1 billion worth of revenue this year.
If it continues to grow its market share so rapidly then it is possible that it could impact on Google's advertising revenues and permanently supplant it at the top of the internet pile.
