> I just want an online service that will generate a new credit card number for me on demand.

I'm wondering why it's not more widespread. My (small) bank has been providing me a unique card number for every purchase for at least the last 5 years, and they're not usually on the cutting edge regarding banking technology. You can also give a maximum amount that can be withdrawn on the card, and once someone has withdrawn money using that number, no one else can do it.