[nickonline]

In a world with fast payments, that money can be washed and moved and out a dozen atms quite quickly

[lukeschlather]

That's why payments typically take a few days to clear. Bitcoin is designed for instantaneous payments with no rollback, which is an anti-feature.

[gizmo686]

Bitcoin explicitly does not have instantaneous payments. The standard view is to wait for 6 blocks before considering a transaction as "confirmed" Confirming a transaction at 0 blocks leaves you open to a very low cost double spend attack.