My guess is that it depends on your business model. (1) The risk to a TPPA model would be a fraudulent payment merchant signing up with your service buying fro

My guess is that it depends on your business model. (1) The risk to a TPPA model would be a fraudulent payment merchant signing up with your service buying from themselves with stolen cards. Charge-backs would occur here once the card owner discovered the card was stolen. (2) The direct sale model risk would be selling and delivering a good or service and then the card holder (stolen or otherwise) charges-back to get the good/service for free. In case (1) fraud detection would help detect the stolen card and mitigate the risk. In case (2), legitimate charge-backs from non-stolen cards are probably sometimes the bigger risk. I most likely didn't hit all the cases here but it certainly seems to be the case that PayPal or the like would not always help your business model with fraud prevention, supporting what callmeed said here.