This is a quote from the book "On Zero Confirmation Transactions" by Chris Pacia
...round the network (double spends were not previously relayed and would not reliably propagate the network). With double spend relaying a retail point-of-sale terminal could have detected a doubl
e spend attempt and flagged the cashier to halt the transaction. The screen might read ‘payment declined’ and the customer asked for another form of payment. Should the original transaction
actually confirm, the retailer could just refund it. The patches actually got merged into the codebase but, of course, the usual suspects bitched and moaned about ‘encouraging people to rely o...
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