Hmm. So, perhaps credit cards should take the same view. Nobody's going to bother doing a fraudulent charge for just $5. We'll just stop checking those. The 0.1% of people who would do that can now do so freely, and our system will make no attempt to stop them.
To what, exactly, do you think that will lead?
It's not exactly the same. The system will still look if at present you have enough bitcoin to cover the cost.
Zero Confirm just means it's possible that another transaction could be introduced before the original transaction gets "committed" to a block.
So, the scenario would be. You pay with your bitcoin at mcdonalds, system checks says yeah they got enough to cover this, but since the mcdonalds transaction has zero confirms it's not "commited'. So, you then immediately run across the street to the alcohol store snatch a bottle of vodka, and attempt to pay for it. Well, most likely it'd be blocked because you can see uncommited transactions on the network, so there provider will most likely block it.
But it is possible for a short time frame that a double spend gets introduced, in that scenario whichever transaction gets committed first would be the one that actually gets paid.
So, first it's not very likely you'd be successful to begin with, seeing Mcdonalds will be using a payment provider like coinbase or similiar and they monitor pending transactions. Second, you'd only be able to do it for cheap stuff, ONCE at any particular store. Any large purchase would require at least 1 confirm on the network, and the higher the cost the more confirms. Third, the longer you are at the location in question the GREATER the odds the double spend will be discovered from the other purchase. So, better get in and out quick or the cops will be called before you get out of the parking lot.
So, yeah, you'd have some percentage chance of getting one of your two transactions for free potentially. A coordinated attack with another person timing the swipes together would probably gain you the best odds. So, you swipe at mcdonalds, and I swipe at Burger King I suppose at the exact same time, and you'd probably have a small amount of time to escape. Unless of course Coinbase handles both Mcdonalds and Burger Kings transactions then they'd know instantly. So, make sure each business is using different providers and aren't sharing transaction data with each other to prevent double spends.
Anyway, but yeah it's possible to some degree. Not worth it though for 99.9% of the population, you'd be better off getting a minimum wage job, you'd do better.
