I think you can buy BTC using your prepaid card

What country?

We've look at allowing this, but, how do you differentiate a prepaid card from a standard bank card?
Do you simply take the users word on this, and allowing them to choose the type of card it is their using for purchases? As of now, this is not really an option for any Bitcoin related business model.

You can do it following the guide on my signature. You won't be risking anything because you won't be buying bitcoins directly (read the guide). Initially, your purchase limits with credit cards will be low. That's because of the huge amount of frauds involving "intangible" items purchased with PayPal and credit cards. BTW, prepaid cards will work just like normal credit cards anywhere. After you've made your first credit card deposit, your limits will increase with time. Fees are also high at first, but they will also get progressively lower. Note that you don't need to use PayPal, you can use your cards directly.

did you searched here https://en.bitcoin.it/wiki/How_To_Buy_Bitcoins_With_Your_Credit_Card?

it should work with circle too with prepaid card that don't necessarely have a bank account attached, like deutsche debit card