This is fascinating. According to this story on the BBC, the Danish prime minister  Anders Fogh Rasmussen is the most popular European politician, and only just behind Arnold Schwartzenegger in the number of friends he has.  This is of course on Facebook http://news.bbc.co.uk/1/hi/world/europe/7355434.stm
I posted a week or so ago on government in chatrooms and egov wanting to get where the citizens are by engaging in chatrooms, online discussions etc.  http://www.thoughts.com/rose22/blog/government-in-chatrooms- intrusion-or-good-egov-83630/  As you may recall, I think there's a good possibility that we get carried away with the technological possibilities out there and forget why people get involved in social networking in the first place - i.e. it's social not just about information.
Strikes me that the Danish PM, arranging to meet and go jogging with his Facebook friends - around 85% of whom are in the crucial 18-34 demographic and are not usually party politically active - might have come up with a good way of linking digital interaction with real face to face engagement. 
There's a bit of a buzz about another social networking site - Twitter.  Users are sent "tweets" - little 140 character text message style updates - on what their friends etc. are up to.  I'm steering clear for now.  the temptation to check Facebook too frequently is already there, and a site which sends the status updates straight to me would make it hard to get anything done at all. Also seems a bit more about putting info out rather than interaction on my terms.  But if you are interested, and people interested in politics seem to be, Number 10 apparently has a Twitter channel. 
Although I love Facebook and rarely touch my Bebo account, the best at the moment for me is Linked-in.com.  Linked-in is clear about what it's for - there's a clear helping you build your work networks ethos.  No difficult do-I-want-to-be-friends: for example if a colleague is a friend on Facebook they can see your drunken photos or your silly status. But if say an ex contacts you on that site it's for your usefulness as a contact and nothing more. And that's a relationship you can live with and respect.