There was not long ago a very similar service which has turned out to be scam, unfortunately, hence you should expect a lot of questions.

For start, I've seen some things you may want to clear up:

1. You say you don't ask for identification, still, at account creation you're asking for First Name / Last Name.
Do they have to be the real name?!

2. From what I know, at least in Europe, Mastercard doesn't issue anonymous cards with amounts bigger than 250 EUR (iirc). Yours easily go bigger.
Are the cards indeed anonymous? And if so, how can you guarantee an user doesn't lose his money because Mastercard has closed his card?