[encoderer]

You only need to convince the payer. The recipient gets an email that says "You have money waiting, let us give it to you."

[mahyarm]

No, they then tell the payer, pay me with this instead, I don't want to sign up for this. The usual use case is giving money back for restaurants and such, so you have the social closeness to do this.

[weixiyen]

FB is in a unique situation where they can convert at a pretty high rate.

[robryan]

Seems to work pretty well for PayPal.