I wonder if this is why I had two teen-porn membership charges to my Mastercard recently.

Really pissed me off. I had the card changed
immediately.
Everybody . . . use Shopsafe whenever possible. It's lightning fast, spits out a virtual card number in seconds, lets you assign a maximum amount, and lets you expire the number in one month.
It's particularly useful for cyclical charges, such as an over-ambitious internet provider you wish to try out for free for, say, 3 months . . . and then foreclose them from "accidentally" (yeahright) continuing to charge you after you've cancelled. Oh and, they won't be able to tell it's a virtual number.

Loads o' fun. Best thing since the invention of Lycra LOL.