An Ethereum soft fork, to prevent DAO money being taken, would permit a DoS: https://hackingdistributed.com/2016/06/28/ethereum-soft-fork-dos-vector/ (the system complexity here is huge)
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I'm amused to learn that many MUSHes have a notion of in-game currency used to pay for compute: https://github.com/pennmush/pennmush/blob/master/game/txt/hlp/penntop.hlp#L794
This very much predates Ethereum or AWS Lambda pay-per-API call!
Panopticomputers: Code Execution Courts for Scalable, Decentralized Computation https://medium.com/@simondlr/an-intro-to-truebit-a-scalable-decentralized-computational-court-1475531400c3 (Ethereum could compete with AWS!)
Monads provide explicit sequencing. A pure language with monads would be a great for Ethereum (though smart contracts would still be scary)