0-confirmation transactions for small purchases

[DiThi]

I'm opening this thread to continue a discussion started in this other thread.

I think 0-confirmation transactions are safe for small purchases if the merchant have a transaction radar connected with hundreds of nodes across the globe and waits for e.g. 80% propagation with no other conflicting tx.

I've done purchases of 1-2 euros with credit card, and just the fees are far more expensive than the possible double spends undetected by a tx radar.

What do you think? Has anyone tested this thoroughly?

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[Maged]

What do you think? Has anyone tested this thoroughly?

Not in reality. However, it can only ever be a problem if ALL of the following are true:
1) Purchaser is anonymous. (real life isn't anonymous, since it can be recorded with a video camera)
2) Item is irrevocable/irretrievable. (you could buy a video game license instantly, without risk to the publisher, because it is revocable)
3) Transaction is instant.

As you can see, there are many cases where instant transactions have little/no risk. If all of the above are true in a specific case, however, you better make one of the statements false if you don't want to get burned.