Or are the individuals responsible only once they get caught?
Nope, it’s just like a charge card that you would procure. From the federal travel regulation:
Cardholders are personally responsible for all items billed to the card, unless the card was reported lost or stolen. Employees shall pay the contractor in accordance with the contractor bank payment terms. These responsibilities are explained in the Cardholder Agreement that each employee signs during the application process. Furthermore, employees are not relieved of their obligation to pay the travel charge card bill in those rare instances when the agency has not reimbursed the traveler within the 30-days after receipt of a timely submitted voucher. (FTR 301-52.24)
Where the regulation refers to reimbursement they are referring to the per diem allowances, air fare or mileage, rental car expense and hotel costs that a traveler may claim.
You have a point about the cost of the investigation, but the fact is that these folks are violating the law, it’s just that the violations actually cost taxpayers zero.
I believe the only reason it’s an issue is that part of the contract with VISA is to hold down the incidents of individuals defaulting on the cards.
Or are the individuals responsible only once they get caught?
I guess the answer is neither, remember the defense department lady who paid for her daughters ten thousand dollar wedding and the one that bought herself a new mustang. Rumsfeld never fired either one as far as I remember.