Zero-confirmation Bitcoin transactions
zerocharactersleft.blogspot.com
zerocharactersleft.blogspot.com
One online gambling site that accepted zero-confirmation transactions was burned by double spends. The bettor would quickly respend any funds they lost, invalidating the payment. If they won, they let the Bitcoin transaction go through and accepted the winning payment.
This new "zero confirmation" scheme wouldn't protect against that. It would just prevent placing a bet, winning, accepting the won amount, then canceling the original payment.
Back to the drawing board, zero-conf people.
Note lines 90-95, the comment explains when coins will be forwarded and how to change that behavior
It's a pretty neat trick to extend the "all or nothing" property to multiple transactions. For some very limited use-cases (like my admittedly contrived example), this is exactly what you want. Usually it's not. Usually you just have to wait.
Honestly, bitcoin is not really suited for instant gratification things.