Interesting that the Beeb have got their Web 2.0 thinking hat on and have started adding bookmark links at the end of each news story which link to Delicious, Digg, Reddit, Facebook and StumbleUpon really easily. Clicking through to "What are these?" gives their explanation. They've included different types of Web 2.0 community sites depending on the type of story and/or user.
It's a audience play - helping to spread the content and promote themselves on other sites. I do like the Facebook feature and in fact I might have to do something like this on my blog! :-)