Comment *US Passport Cards*, not real passports (Score 2, Informative) 251
It's absolutely worth noting this is about cloning US Passport Cards, which are completely useless outside the US, not real passports.
Passport Cards use a simple RFID system (EPC) where the chip simply spits its ID number out.
Passports, on the other hand, require a reader to authenticate by passing a hash of (passport number, date of birth, date of expiry). I don't think that's nearly enough information to ensure security, but at least it's better than nothing.