LinkedIn and IBM, for example, intend to make it easier for users to access their social networks from other Web services and applications. Multiple services on the Internet, among them Google-sponsored Socialstream, claim to be able to allow users to post content and then syndicate it to a variety of social networks where the poster may have a profile. LiveJournal already supports single-sign-on system OpenID. IBM's even talking with "a lot of the major social networks," presumably including Facebook and MySpace, to see how they might work together and share information with one another.
But social networks are a long way from standardizing features and communication, which may be a necessary step for widespread sharing of information. The haphazard scaffolding of social networking means there are no cross-network standards for profiles, for feeds of information coming from users' contacts, or for the way "friending" someone is handled.
Even the very definition of a social network isn't exactly perfect. They typically contain profiles, some ability for a user to connect themselves to others, some search functionality, and the ability to communicate with other users. However, that's not always the case.
Meanwhile, Facebook, as well as some of the other social networks, are relatively closed to the outside world. Everything there happens within a Facebook bubble where any communication has to happen between registered Facebook users. Facebook profiles aren't fully indexed by Google.
There are certainly possibilities. Something like Microsoft's CardSpace could act as a cross-authentication mechanism, while OpenID could be a single sign-on. RSS could be the standard for feeds of information. Still, even if the technical challenges are solved, there's a bigger sociological and privacy hurdle. And there may always be the tricky problem of Web identity -- you can still be a dog and have nobody know it on the Internet.
For now, Plaxo's Pulse might be an indication of where social networks are headed: user control. Plaxo puts the user at the center, basing the network on Outlook contacts rather than who's a member of the network and includes feeds of information from places like Flickr photos, YouTube videos, Amazon wishlists, and LiveJournal postings. The company even recently introduced a LinkedIn synchronization and de-duplication service for its own platform, allowing the Plaxo rolodex to grow with a user's LinkedIn contact list.