"Standard" debit cards aren't really standard outside the US either. Maestro (chip + PIN) doesn't work online, for example.

My VISA (chip + PIN) works without any problems for online purchases. Some sites even transfer me to my bank's payment gateway that sends me an SMS with a number in order to be able to pay.

I don't have a credit card. I know a lot of people who does but rarely uses them, debit cards feel more secure than credit cards against theft/fraud (and I'm not really sure if they are, I don't think so).

Debit cards aren't more secure again fraud. If anything they are less so. Much easier to refund a transaction on a CC.

My VISA ... I don't have a credit card

Visa is a credit card, however. In Europe, it's often tacked onto a regular debit card, but it's a separate thing not everyone has.

You can get "Visa Debit" cards

I'm intrigued. What bank does that?

It's called 3-D Secure. (http://en.wikipedia.org/wiki/SecureCode)

You usually can use a Maestro card online. I think at one point they rolled 2 different cards into the Maestro name which included one for younger people which is supposed not to work online (which would disallow FB payments as well).

In europe certainly most people would seem to have a debit card. Besides I'm assuming at the backend the FB system would require you to enter a debit/credit card.

It would seem very unwise for FB to begin taking down everyone's bank account number as in the case of fraud with a card you can simply cancel the card and get a new number.

But coincidentally is a standard enough debit card that I can use it to pay in stores all over the world. Even the US.

Maybe in the US.

In Brazil, I do not know a single debit card that will allow international purchases, or that will be allowed in Paypal (even though Paypal has a local presence).