Don Reisinger sums up a Pew report:
According to a Pew Internet Personal Networks and Community survey, which polled 2,512 adults, the dawn of new technology and the Internet has not caused people to withdraw from society. In fact, the study found that "the extent of social isolation has hardly changed since 1985, contrary to concerns that the prevalence of severe isolation has tripled since then." Pew said that 6 percent of the entire U.S. adult population currently has "no one with whom they can discuss important matters or who they consider to be 'especially significant' in their life."
That said, Pew did find that Americans' "discussion networks"--a measure of people's "most important social ties"--have shrunk "by about a third since 1985" from three people to two. However, Pew found no evidence to suggest that it had anything to do with mobile phones or the Internet. In fact, the organization's study found that mobile-phone use and active Web participation yields "larger and more diverse core discussion networks."