While I'm disturbed by this story, I'm more disturbed by many of the comments attached to it.
When people meet over the Internet otherwise, no one sues the ISP. When people take out ads in newspapers and talk on the phone, no one sues the phone service. The end result is that Microsoft cannot be held accountable for this sort of thing, and anyone who knows me knows I'm no fan of the big MS.
The future is now, and that means that no one is particularly safe. Communication is instantaneous and everywhere, and parents will need to be more stringent if they wish to protect their kids. You can't be everywhere, but that doesn't mean you shouldn't be keeping tabs on them.
I dunno. The world's a lot bigger now, and everyone's still within reach. That's going to change a lot of things in the long run.