It's called MyChurch.org, and its primary purpose is for growing church communities and reaching out beyond the usual choir: "This is not 'MySpace for Christians,' this is MyChurch for everyone. All are invited, come as you are... be yourself. When and if you're ready to look for a church, browse around the different church communities in your area or check out the churches that your friends go to."
It's still in beta, but an interesting concept.
There's even a lively debate about the MySpace and Comscore numbers on the Church Marketing Sucks post about the subject.