Preferences aside, PayPal runs the disclaimer because it just happens to be illegal. Whether anyone likes it or not is beside the point. Of course PayPal doesn't care one bit what people do as long as they use their services and someone pays whatever fees they, or the credit card companies, charge. They make folks agree not to pass along the fee so that they can say to any authorities who may (or may not) investigate their compliance with the law, "hey, we told them it was illegal, we told them not to do it, and they agreed -- don't look at us." This will likely serve as enough of a complication to diffuse any interest in enforcement against PayPal, and there is certainly no political will, advantage, or practical feasability in enforcing it against individual users (...yet, with more high-volume or institutional users, I guarantee this will change).
Consequently, whether or not folks insist on passing this fee along to purchasers is a question of nothing more and nothing less than their own integrity. In fairness, most individual sellers likley don't realize what is at issue. Notwithstanding, no one who insists on passing a surcharge for a service they have selected for their own convenience is someone I would elect to do business with -- and the fact that they do so illegally and in clear breach of an express covenant only drives it home further. I don't think it's worth getting particularly exercised over, just not transactions I need to be a part of. As in all things, the choice is yours.
