Isn't that exactly how those bitcoin debit cards work except the price tag is in btc?
Chemistry, do you have some links about these credit cards ?
I understand well bitcoin, since I'm porting the code into C#, but lack knowledge on the ecosystem yet.
I have not checked very deeply, but to my knowledge, all of the bank/exchange I've seen like Mt Gox, Coinbase, BitPay, they all give you a BTC account, but without you having the private key.
This means that the amount you see on their site web is no different from fiat currency since they don't have to keep the money in the vault.
Are these credit cards not just credit cards on the fiat currency account they show you ?