• by Mark Walsh  @markfwal, August 3, 2010

The Nielsen findings released Monday showing share of time spent on social networks and games blowing way past time spent on Web portals are a harbinger of things to come in mobile.

Portals are still the second most popular online activity in mobile behind email, but social networks are closing fast. Social networks account for 10.5% of time spent on the mobile Web, up from 8.3% a year ago, while portals have slipped from 14.3% to 11.6%. So the zero-sum game playing out on the desktop between social sites and portals is mirrored on mobile devices.

The surge of social networking on mobile phones cited by Nielsen echoes research this spring from comScore showing social networking to be the fastest growing mobile content category in terms of audience, nearly doubling in size through the browser, and tripling via mobile applications.

Facebook alone has more than 150 million active mobile users worldwide and says mobile users are twice as active on the social network as desktop users. The rise of Twitter, Foursquare and numerous other social properties geared to mobile devices and location-based services ensures that the link between handsets and social networking will continue to grow.

Further cementing the relationship is the spread of smartphones, which have reached 25% penetration among U.S. mobile customers, according to a separate Nielsen report. This report also reiterated the prediction that the share of smartphones will outstrip feature phones by the end of 2011.

Email is still the dominant mobile Web category, even increasing share of time spent to 41%, up from 37% in the last year. But as social networking continues to gain share in mobile, it seems likely email will decline over time in mobile as more people message within Facebook and other social sites at the expense of email.

Online games is one category where there's still a sharp contrast between the PC and mobile phone. Games moved past email to claim the second biggest share of time spent on the desktop Web, at 10.2%, but was only the 11th most popular mobile activity in May, with a 1.7% share, according to Nielsen.

That low figure may be in part because the firm isn't counting games accessed via applications. Games, for instance, dominate the lists of top-paid and top-grossing titles in the App Store.

But as Nielsen analyst Dave Martin noted in a blog post Monday, how people interact with computers and mobile devices is still not quite in sync. "While convergence will continue, the unique characteristics of computers and mobiles, both in their features and when and where they are used mean that mobile Internet behavior mirroring its PC counterpart is still some way off," he wrote.