What is Social Networking in the Digital Age?

Now and again I struggle for a good working definition for Social Networking. There was a time when Social Networking simply meant knowing people in real life so that you could call on them if you needed something. You would go to parties, get introduced, participate in clubs or sports, and generally be friendly. The bigger your rolodex was the better.
The same paradigm exists for social networking in the digital age, albeit far more abstractly and more compartmentalized. When people talk about social networking today, they typically are talking about using some networked service to build online social networks. These services provide communities of people who share interests and activities or who are interested in exploring the interests and activities of others.
In general a social networking service allows users to create a profile for themselves which is shared with others using the same service. Users can often upload a picture of themselves and select other users whom they wish to be "friends" with. The second component of a social networking service is the ability to share something. This might be commentary, news, pictures, movies and so on. These two components must be taken together to form the definition of Social Networking in the digital age. Take away either one and you are simply left with a file transfer service, or a electronic rolodex.
In writing this posting I realized one important thing that is likely shared with a number of readers. It comes from being of a generation who did not grow up with computers and it is the phrase "digital age." For younger generations saying social networking in the digital age is redundant. For them social networking has become synonymous with the use of networked computers.