Localytics said that 20 percent of apps are currently “socially connected,” via either Facebook or Twitter – with the former being by far the most popular option.

Based on its analysis of titles with more than 500 monthly active users during the January to July 2011 period, 95 percent of socially connected apps include Facebook support either alone or alongside Twitter. Twitter is present in 50 percent of socially connected apps, although in most cases it is deployed alongside Facebook – only 5 percent of apps support Twitter alone.

While Facebook is the more popular tool, Twitter drives more traffic, generating 50 events per 1,000 users, compared with 11 per 1,000 for Facebook. But due to the greater penetration of Facebook, this service still generates twice as many events by mobile users.

Localytics also noted that Apple’s decision to integrate Twitter into iOS5 means that “this higher rate of sharing for Twitter users becomes very interesting.” It said that if the combination brings Apple’s iPhone user base to Twitter in large numbers, “iOS app developers may see Twitter swiftly overtake Facebook as the most valuable social integration.”

The company highlighted the significance of social integration by stating that “social sharing can be the most powerful word-of-mouth marketing for a smartphone app, since it carries not only your message but also the approval of your users to their friends.” It can also raise the visibility of apps, which may lead to heavier promotion if a product is seen to be trending.