The Solitude of Social Media
One of the unique things about Twitter in 2006 and 2007, especially during the first tweetups was that it was a network of strangers who became friends without meeting in person. The people I became friends with in 2006-2007 are still friends now, to some degree. I met them every week at tuttle events and tweetups.
At the same time Facebook was a network of friends from university, which then became friends from work, to friends from various activities. These were networks where, in the first case, you met new people, and in the second you consolidated personal friendships in the physical world online.