[runeks]

> What I do not understand is why we couldn't build this onto a web of trust + proof of stake.

Because the incentives of nodes in a web of trust is not to tell the truth about how much money they have; their incentive is to prefer whichever chain says they have the most money.

With proof-of-stake, an arbitrary number of valid chains can be created from scratch in no time. How do we decide which is the right one? All nodes will prefer the chain that says they’re the richest, and the nodes that most efficiently can coordinate their lying will end up with all the money.

Proof-of-stake solves the wrong problem: the problem isn’t to decide who gets to extend the chain, the problem is deciding which chain to extend in the first place (there can be millions of valid PoS-chains).