[NO_CHANGE]

I used to make new virtual numbers from Wamu for each online transaction, setting $ and time limits. Only later did I read that those "one-time" numbers could be charged more than once and the expiration dates didn't matter. That's why I skip this extra useless step these days.

[BHSPitMonkey]

That still gets you the ability to figure out who leaked your card number, and presumably a way to manually revoke the number without hosing the whole card.