Everyone loses in this case. The card is supposed to facilitate a transaction and it failed to do so; the shop went without their money, the family went without their bikes, and all of the various financial institutions went without their cut.

Which is why the poster above is warning about this; if there will be merchants out there who won't accept it, it's pretty much DOA as you can't replace all the cards in your wallet with it.

That's partly what makes this idea such a great bet. It's a positive sign Coin evokes such magnitude of excitement and disbelief.

It's both parties' loss.

Their loss of possibly getting chargebacked? Seems like a benefit.

No, their loss of the sale, obviously.