If you have read one article here about social networks or another, you have learned that that the MadScientist is not necessarily a friend of social networks because I'm just too paranoid to see that many advantages in leaving my personal data and preferences on any servers just to make the providers happy and to simplify their advertizement strategies.
But - and this is the technical part beginning here - you have to know your enemy and the technology he is using. It's not bad to know about weaponry even if you're a pacifist, so let's have a look about recent techniques and trends to come.
What's it about? It is understood that users of social network sites (take anyone you know) want to migrate their data to other network sites for various reasons: because they want to leave one portal and enter another, or they might want to merge their data because MySpace, Flickr, and Facebook just isn't enough and the user is too lazy to type in once more her user data. So what does the industry need, as always when it comes to exchanging data? A standard, right!
According to this article (paid subscription req'd) by Karen Heyman, several techniques are already available that might be part of a future standard for exchanging user profile data between various providers: RSS, the Really Simple Syndication for exchanging syndicated content; OpenID, an identity system supported by some big players (Google, Yahoo, Microsoft), in order to enable users to register accounts without having to re-enter account data; OAuth, a protocol for secure API authentication from various sources; Microformats integrate meta information in HTML containers, thus adding semantic data to it; RDF (Resource Description Framework), another method of modeling information that adds metadata to content; APML, "an XML-based format for capturing a person's interests and dislikes" (Wikipedia); SIOC (Semantically-Interlinked Online Communities Project), a semantic technology for interconnecting web-based discussions (blogs, forums etc.); FOAF (Friend of a Friend), an RDF extension for "describing persons, their activities and their relations to other people and objects".
Several of these technologies are used by the DPWG who wants to give to the users control over their data. A lot of the logos you might have seen at the Wikipedia links above can also be found on DPWG's homepage. But, according to their web site, they don't prefer one technology and neglect the other but they promote and moderate in the desired standardization process. No wonder you find them on a lot of conferences and barcamps. Microsoft and Google are already members of DPWG.
Emerging standards, international enterprises with profit-oriented long-term goals, careless users and a vanishing awareness for privacy issues will set up the scene for the next following years. This is not only a 'digital' phenomenon: debit cards that allow customers to save a few bucks are also a perfect means to collect customer data and use their preferences for creating profiles. With powerful standards the exchange of all these data will be made simple, giving web users and customers a feeling of being well-known and, maybe, liked. Difficulties when trying to hide your identity will amplify until it will be completely uncommon to have a desire for (online) privacy, at least recent developments in politics suggest this. The data collector's club is still growing and there are several good reasons not to give your data away.