[lelio]

Instead of going for a direct attack, the terrorists could do something like find a hacker with a bunch of credit card numbers (like that one that supposedly had 300k of them from CD Universe) and publish them on the web. Pretty soon every krad d00d and his brother will try and use them, clogging up Visa's and MC's computers with bogus entries. Merchants will be leary of accepting any credit card. yada yada yada

[Cachelot]

the terrorists could do something like find a hacker with a bunch of credit card numbers (like that one that supposedly had 300k of them from CD Universe) and publish them on the web.

Wouldn't work. The kiddies do that sort of stuff all the time, and the card companies do have pretty good stoppers in place ;).