For sure. Most businesses would be happy to pay a dollar or two for traffic sent their way from various channels, including some kind of directory with reviews

For sure. Most businesses would be happy to pay a dollar or two for traffic sent their way from various channels, including some kind of directory with reviews. You just need to show proof that a given customer came from that directory. A single-use coupon code springs to mind, a fake phone number (one per directory service per business), bounced links embedded inside driving directions, direct link to a page where one can order or reserve a spot and such, etc. Anything that attaches a token to a user will work as a proof. It's all possible, but simply asking for $100 is a lot easier because the power disparity is so huge. Then there is the fact that is Facebook ever shows interest they can easily crush the entire market - they don't need to make immediate money and the identity of the reviewers is better known, providing higher quality score.