Interesting research on the dynamics of online and offline social networks.  Seems like our close connections undergo some pruning as time passes.

You may have more Facebook friends as the years go by, but when it comes to your close friends, you lose about half and replace them with new ones after about seven years, new social research suggests.

As a result, the size of your social network stays about the same.

Also, social networks don’t seem to be shrinking as previously suggested and apparently context dominates over choice when building your network.

The results showed that personal network sizes remained stable, but that many members of the network were new. About 30 percent of discussion partners and practical helpers had the same position in a typical subject’s network seven years later. And only 48 percent were still part of the network. This finding goes against previous research which had showed that social network sizes are shrinking.

Mollenhorst also established that networks were not formed based on personal choices alone. Our friend choices are limited by the opportunities to meet. He saw that people frequently choose friends from a context in which they have previously chosen a friend. Also, whether or not our friends know each other strongly depends on the context under which people meet.

via Half of All Friends Replaced Every 7 Years | LiveScience.