I have never heard of this sort of open answering service. It sounds like a good idea, I like the way with a current question those answering can bounce ideas off each other before someone puts in a final answer.
It makes it hard to conduct a reference interview though. As I'm sure you are aware a lot of the time people don't know how to ask for the information they really want.
I can see how librarians on the ref. desk could use some of their time to help answer questions, but when would we get the time to do our 2.0 course?