I have to confess that I have been mostly a passive user of services such as Facebook and LinkedIn in the past, but I’m finding them more useful lately, and I’m also intrigued with the any-to-any connection scenarios supported by Microsoft Windows Live and many other services.
An example I noticed today when I logged into LinkedIn:
This is a bit subtle, but it basically means some of the leading services have made it possible to track your assorted contacts in a service-independent manner. You could, for instance, track the activities of and updates from your LinkedIn or Facebook contacts in the new Windows Live home page, or (at some point in the near future, I assume) vice versa, if you want to track activities across multiple services from a single place.
If this sort of service aggregation view becomes popular – and I expect it will, as it’s a means of gaining more control over the multiple update/etc. communication channels -- it will put increasing pressure on social networking service providers that can’t readily differentiate themselves.