[Cryptography] Robust Linked Timestamps without Proof of Work.

[John Levine]

>Bitcoin chooses to make that trade-off, giving its users the option of an
>irreversible payment system. This is a good thing, because for some use-cases
>the downsides of reversible payments are worse than the benefits (for many
>merchants a significant amount of fraud happens due to reversibility).

Indeed, although it you want to make irreversible payments now, you
can do that with envelopes full of cash.  Hardly anyone does, at least
for legal purchases, which suggests to me that there isn't much of a
market for irreversibility.

R's,
John