2) What non-mining full nodes add in practice - Define the …

2) What non-mining full nodes add in practice
- Define the payoff surface: By refusing to accept invalid blocks/txs and by not relaying them, they ensure that “longest chain” isn’t sufficient for economic finality unless it also satisfies the rules those nodes enforce. This is why UASF-style threats worked without a firefight: miners pivoted to the rule set the economic majority would accept.
- Reduce collusion risk: If the network were mostly SPV (longest-chain followers), a majority of hashpower could more safely change rules; with widespread validation, such a move strands their coins.
- Network resilience: Independent nodes diversify propagation paths, making censorship/eclipsing harder and double-spend detection easier at the edges. They’re not in the block-production path, but they shape which chain is economically usable.