Even if one concluded the transacting participants only have an altruist-prime incentive to do validation spot checks, it is not an undersupplied public good[^subjectivity] because there is no practical incentive, nor plausible way to verify and pay participants, to not do it. It seems plausible that there is the additional motivation of jealously (aka crab bucket mentality[^crab-mentality]) in that any participant or faction wouldnt want to allow any other participant or faction to be able to cheat to obtain an (especially non-meritorious) advantage. A generative essence that seems to drive the viability of decentralized systems is that if no factions are powerful enough to overcome the checks of the other factions, then the resultant Nash equilibrium is a stalemate that preserves decentralization and meritocracy, which is the antithesis of a power vacuum such as is otherwise the case with politics and democracy.[^ESR] [^voting]
Byzantine fault tolerance allows individual nodes to assess whether another node is behaving out of the ordinary in relation to the rest of the network and thus ignore that misbehaving node?