Americans are spending more of their internet hours on social networking sites, according to a survey by The Nielsen Co., and less on such traditional activities as e-mail or portals.

It is, it would seem, another data point to buttress a long-evolving argument that social media is displacing e-mail marketing.

But consider this: Nielsen also found that the way U.S. consumers are spending their internet time on their mobile devices still reflects more traditional patterns. There was a double-digit (28%) rise in the prevalence of social networking behavior among mobile web users in June 2010 compared to June 2009 - but email activity on mobile devices remained the dominant activity with an increase from 37.4% to 41.6% of U.S. mobile Internet time.

Portals remain as the second heaviest activity on mobile Internet (11.6% share of time). Other mobile internet activities seeing significant growth include music and video/movies, both seeing 20% plus increases in share of activity year over year.

Social Networks Grab 22.7%

Still, though, the main findings of its report, highlight the ever-growing popularity of social networking and the ripple affects that popularity is having on other internet trends. Americans spent 22.7% of their time online on social networks and blogs in June 2010 - up from 15.8% in June 2009, for a 43% increase. Gaming was the next most popular activity online, with U.S consumers devoting 10.2% of their online time to it, compared to 9.3% a year ago. E-mail, by contrast, dropped from 11.5% to 8.3%.