It may not be very trendy to say so, but my reaction to this news is: good!
Although it's possible to imagine circumstances in which this information could be abused, anyone who wanted to do this already could (if you seriously think the Security Service - MI5 to you - couldn't get this information if it wanted to, you're deluding yourself). I'm far more concerned about the effect this will have on perceptions of the internet, and as far as I'm concerned, they're positive. When we all lived in small rural communities, we were subjected to this level of scrutiny all the time - it's called social cohesion. The idea that the internet is a complete free for all where anything goes is dying. Good.