Venmo is already trying to solve this by incentivizing users to flag payments themselves. When you go to pay someone, there's a pretty big box on the screen th

Venmo is already trying to solve this by incentivizing users to flag payments themselves. When you go to pay someone, there's a pretty big box on the screen that says "Are you paying for goods or services? Protect your purchase here" with a little toggle button, and an explanation that the seller will pay a fee in return for you being able to get a refund.