An excellent idea.
The problem is assembling a "quorum", a number of people interested in interacting with the salesman at the same time. There are similar things in customer service chat services, but that's one on one and not with a salesman.
Another issue is that people tend to be rude on those things. I can see a Chevrolet partisan calling a Ford salesman something pretty bad.
I don't think it would work, and I think it's a good idea. No one would have to go there.