[Cryptography] Proof of Work is the worst way to do a BlockChain

[Allen]

> This is a WKBI.

What is "WKBI"?

> The original proof of work idea to deter spam was
> Dwork and Naor's Pennyblack in 1992.  While it was certainly clever,
> it didn't work and doesn't work.  I ran into Dwork at a conference
> some years later and she agreed that it's too easy to circumvent.

Are you referring to the idea of hackers remotely compromising a bunch
of computers and using them to compute PoW?

Are there other methods to circumvent PoW (in the context of spam), or
is that it?