It does make a difference dealing face to face as Bill mentioned. When I'm doing test rides, I leave the shop on the sale bike, and the prospective buyer rides his own (trade-in scenario). The we get a couple miles out, and we switch. He gets the feel of the new bike, and I get to scope out his trade-in.
For a used buyer, it's common for an owner to not allow test pilots. I have 40 years and half a million miles under my belt, but that's how I bought my RC51. I drove 3 hours on speculation based on what we had e-mailed back and forth and telephone calls. Still no test jockey ride, he was adamant (for all he knew I was full of crap about my riding credentials right?). By the time I was done with the visual/tech inspection he realized that I was no dummy and he said if I wanted to take it for a spin I could. About then the sky opened up and a deluge ensued so I paid him his coin and we loaded the bike in the truck and I headed for home.
Most owners need to feel some sense of confidence in a prospective buyer before allowing anyone on the bike let alone operate it solo, I know I do. If I ever were to sell my RC (or my Wing for that matter), the first thing out of my mouth after asking the buyer's age and experience, would be a refusal of a test ride. He'd have to earn it, and there'd be coin in my hand and a bill of sale in his prior to departure. And I'd still be riding along with them.