This is a quote from the book "On Zero Confirmation Transactions" by Chris Pacia
.... So, at least in theory, the opt-in shouldn’t totally destroy zero confirmation transactions. But the intent is clear. The goal is to eventually eliminate the opt-in part, this patch is just to get the foot in the door.

Once zero confirmations transactions are totally destroyed, you will only be able to transact with a retailer by using one of the quasi-centralized, thi
rd-party solutions that these developers are hoping to profit from as a replacement. That is, if retailers still bother with Bitcoin by that point....
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