Well, Jack, I also don't think they'd sue an agent in Illinois based on what they read on Trulia, but maybe you want to try to establish a precedent?
Here in Washington State, we have two great forms that our MLS provides: one is a Selling Office Commission form, which is an agreement between the buyer's agent and the seller for a commission. The other is a Buyer's Agency Agreement, which is an agreement between the buyer and their agent.
Fair compensation? I think your typical co-broke should be fine. How is it not like any other FSBO?