One major problem I see is how to handle the case when person submitting money later denies making the payment (always an option when you pay with credit card a

One major problem I see is how to handle the case when person submitting money later denies making the payment (always an option when you pay with credit card and I guess quite plausible if everything takes places online). Unless the payment service holds the money in escrow for quite a while, they might end up in quite difficult situation having sent the money forward, but not getting the payment from credit card company. PayPal seems to manage this, but on the other hand they don't hesitate to block the accounts for whatever reason. Sometimes I wonder if this behavior is the reason they have survived in this business.