A few banks provide a system like this. I'm aware of at least Bank of America and Citi. Bank of America calls it "ShopSafe"; you can generate a number for one-

A few banks provide a system like this. I'm aware of at least Bank of America and Citi. Bank of America calls it "ShopSafe"; you can generate a number for one-time or recurring payment with an associated limit and expiration date. Citi calls it Virtual Account Numbers. Theirs don't have a limit by default (but you can create one that does). Unfortunately, both systems use archaic Flash applets to generate and manage the numbers... I hate the Citi one in particular because it has sound effects when you press buttons.