Hitwise is one of my favourite sites for valuable new insights into the UK social networking sites. In a recent post by their Research Director Robin Goad, Hitwise unveiled that Facebook accounted for a staggering 7.14% of all UK Internet visits in June 2010 and well over half (54.48%) of all social networking activity. But the most extraordinary stat was that Facebook accounted for 1 in every 6 page views in the UK making it by far the most viewed site with more than double Google UK’s page views (16.73% for Facebook vs 8.22% for Google UK).

But, here’s the kicker: that 16.73% was actually a decline on the previous month and the fourth month at around this share of page views. Could Facebook have reached saturation point? There has to come  time when people just don’t want to get more of it, and it’s interesting that the average session time on Facebook in the UK has fallen again to just over 27 minutes, down from a peak of nearly 30 minutes in January.

Or is this just a sign of the seasonality we normally expect to see over the summer months? Don’t write off Facebook just yet; we’ve seen similar stagnation points in the past and some of the innovation that’s coming soon could well inject more enthusiasm into Facebook’s vast army of users.