While I was in the Army I had a travel card... pretty much everyone gets one (at least in the commands I was in) and its supposed to be used to pay for official travel related expenses. Limits are set by a persons credit rating etc too at a couple of tiers.

Now, there are a couple of things to the card.. its a normal credit card coloration is very easy to identify, but it is not out of the ordinary for someone to accidentally charge unauthorized materials to the card. If they do they just have to make sure they pay it back. IF they don't pay it back it all gets taken out of their pay.

Now Casinos, There is an airforce base in nevada... near vegas... if traveling out there on official business people may be forced to seek lodging in town for the duration of the trip. There are authorized/contracted hotels that one is supposed to use, but technically if they are full you can go to any hotel and pay up to the perdiem rate for lodging. (if memory serves)

Then there are meals for travel, can be used at any establishment and amounts up to a certain amounts will be covered. Cheese burgers at a vegas stripclub? well technically not the best place to swipe the govt travel card.. but its a bonafide place to go and eat. They also have ATMs for cash advances which are/can be/used to be also authorized up to a point.

I only ever had to use mine for plane tickets and hotels.. but can see how even some minor infractions could be taken out of context. Accidents also happen but there are procedures to get unauthorized charges corrected which arent really all that big of a thing as long as the money gets paid back.

Still cant figure out why someone would use their card in a sex shop.. unless they had snacks or something.