I actually wrote about this the other day: http://whislr.com/2010/04/20/a-different-approach-to-buildin...
I like your thoughts on targeting young professionals, and basing it on an existing network such as LinkedIn also sounds reasonable. Your focus on keeping personal information out of the conversation is not viable - remember, it's not just e-mail and phone numbers, it's also suggestions to meet. I also think that the fee to be hooked up with a second person is going to be a major deterrent.