Most credit cards allow the owner to initiate a charge-back for up to 60 days after the purchase. The bank doesn't ask any questions if the owner simply says it was illegitimate - it's up to the merchant to prove the transaction was a legitimate purchase, which in many cases is almost impossible. I once lost $10000 worth of artwork due to this policy even though I had a swiped card and signed slip. It took me a private detective to prove the delivery address was that of a relative to the card holder, and even then, I had to institute a civil procedure to get the art back. Once all that was done, I laid a criminal charge which was never taken further by the bank or the police. Now imagine dealing with "digital" goods and in which you don't have the advantages of a "swiped" transaction.
I place my little example here to illustrate how difficult it is going to be to create a "fool-proof" method of taking payment, especially with cards and mobile transactions (since mobile companies place the same burdens of proof on the merchant). I fear only mass transactions with transaction fees can buffer the effect of a planned 10% charge-back.  A free or low fee service simply will not show the profits to buffer it's clientèle against fraud and thus, ultimately, find it impossible to survive..