It goes without saying that Facebook is the network du jour, but even though the reigning champion’s user stats keep soaring, social networking as a whole might be leveling off. Nevertheless, there are still scores of other highly competitive social sites that are waxing and waning; and different networks and apps are more popular in specific geographic areas, with certain genders or age groups, and even among various social classes.
For example, Plaxo is the network with the most users over the age of 65. Facebook is more popular with women, but Digg and Reddit tend to be more popular with men. LinkedIn is the “richest” social network, but Plurk outranks it when it comes to well-educated users who have graduate degrees.
They have a ton of traffic data to work with, and this infographic does a good job of summarizing some of the key findings at the top level.