Assuming the hand scan can't be forged or stolen, which is a big assumption and probably not true based on how other biometric scans have failed to be secure, I

Assuming the hand scan can't be forged or stolen, which is a big assumption and probably not true based on how other biometric scans have failed to be secure, I think I would be concerned about revealing too much data about myself. I don't know how 'leaky' the hand print scan is meaning how much MasterCard learns from the scan. But imagine if they could figure out which people were more susceptible to buying say alcohol or coffee when they examine the hand print and then displaying an ad to get the person to make a last second purchase that is targeted to that person. MasterCard can already track your location by seeing where you are buying things and they can watch your purchases which is a lot but who knows what can be learned from a hand print scan. But I think also hackers are very motivated so the security issues are probably understated.