There is a going to be a big business to be built on fraud risk for merchants and stablecoins.

Chasing Curiosity. Pluralist. Empathetic Accelerationist. Founding Fullstack Engineer @icebreaker. YC S16, KB7, fid:66
icbk.me/tayyab.fc

In some cases it is a feature that payments are reversible for a short duration because things can go wrong. 

It seems useful to have an intermediary who can roll back payments if the sender requests it and the intermediary approves.

VC since seven years who likes to write stuff at https://caz.pub

This is how things work in the existing financial system and many consider it a feature so the same feature will probably become ubiquitous for blockchain transactions too.

You would do this on a blockchain by placing the money in escrow and allowing 2 out of 3 to send it back. There could also be a lending component to the system, allowing trustworthy merchants to get their money immediately.