Addressing the "Facebook makes us lonely" meme, Zeynep Tufekci has a fine response:
What data I’ve seen makes a strong case that social isolation is increased by factors like suburbanization, long-commutes, long work hours, decline of community and civic institutions, etc—not online sociality. As I argued, what data we do have argues that social media (and Facebook) works against this[?]..
People who can use the Internet better to find and/or keep in touch with people with whom they share affinities with are more likely to be able to compensate for losing the neighborhood/family ties.
Unfortunately, suburbanization etc aren't very sexy for media panics, showy politicking, and other fearfests.