Corrected entry: Batman couldn't possibly have his own credit card. Obtaining a credit card requires proof of identification and a billing address, neither of which Batman would submit for obvious reasons. And although the Bat-credit card may be a jokey reference to the 60s TV series, Batman still demonstrates his intent on using the card to secure his bid for a date with Poison Ivy, which means that in the context of the film, the credit card is functional.
S. Ha
2nd Sep 2011
Correction: Batman could easily have a corporate credit card from Wayne Industries for personal use. Many companies have cards for employees or even suppliers.
rswarrior