This is scary in many ways. Not so much the photo or the card by themselves but put together they could really give you big trouble (in little china?
)
On a serious note though this could be something new? as has been pointed out, figure out how much you're worth + incriminating evidence = you having a big bill or at least having to keep the girl sweet until she moves on (if ever).
The way things are going with facebook, google+ and other social network tools (linkdin?) could make things like this more common in the future. this is proof why having a punting identity and ensuring that you keep all 'real' details out of reach is so important as it could come back and haunt you.
Regarding the punting cards - great idea but the problem happens when SO's find them and wonder why you have a stack of business cards for the same fictional person? Good reason to stick to incalls (unless you know and trust the girl) and only take basic necessities with you (punting phone, money etc.)
Stay safe out there