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If I walked into a cafe where nobody knows me, got a coffee, and sent some BTC using a personal wallet - don't you think the owner would want to wait for confirmation before letting me leave? Wouldn't I have to wait at the door for 10 minutes awkwardly holding my coffee?
That's the point I'm trying to make.
No.
Once a transaction is in the network (less than a few seconds - usually less than a second it will have reached a vast majority of the network, if not all of it), with a fee and no other problems, it will confirm and a double spend would be rejected by the majority (or all) of the network. Plus the cafe operator would likely be informed of the attempted double-spend. And for a cup of coffee, the cost of a double spend (if even possible) and other attacks would far out-weigh the reward.
The repeated "bitcoin transfers are too slow" comments are from people who either are uninformed about the bitcoin network or are purposefully trolling. There are hundreds of threads discussing why this is a misconception. (Plus as others have said, there would likely be video evidence of who you are in the store so if you tried to steal the coffee, the police would get involved).
