From [Design Rationale](https://github.com/ethereum/wiki/wiki/Design-Rationale):

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> One weakness of the account paradigm is that in order to prevent replay attacks, every transaction must have a "nonce", such that the account keeps track of the nonces used and only accepts a transaction if its nonce is 1 after the last nonce used. 
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There have been some questions on this site about transactions nonces that are too low. What happens when a transaction nonce is too high?