Why not just be upfront and advertise your fees openly?
I haven't tried this or Venmo but I think it would be cool if they added some sort of group portal service, where you could email a group of friends, say for "Dinner: $96", and then Mint would email all of them with a link to a spreadsheet/form of some kind where they could list what they've already paid each other, other related grievances that would affect how much they owe, etc. And then once all had approved the resolved list of payments, the process would proceed on an individual level as normal with the correct amounts.
Why would I want to pay for the privilege of transferring money?
Now if it'd make international transfers easier... But still, $0.99 is pretty steep IMO.
It looks like there's a decent chance that there is no service whatsoever behind the interest-collection and survey. Not a bad strategy for gauging interest, I guess.
Something like this would be extremely helpful for situations like multiple couples renting a beach house or people chipping in for an expensive gift for somebody else.
This tech looks really useful for lots of verticals, but not for friends. If you constantly pay for people who won't pay for you, stop doing that.
" Thanks for your interest in Mint PayBack!
We're still in private beta, but we'll notify you as soon
we launch to the general public. In the mean time, help us
shape Mint PayBack by completing this short survey."