Block Quote: 823815

'There's no need for reporting of "proof of double spending" like that. If the same chain contains both spends, then the block is invalid and rejected. 
 Same if a block didn't have enough proof-of-work. That block is invalid and rejected. There's no need to circulate a report about it. Every node could see that and reject it before relaying it.' November 17, 2008 - Satoshi Nakamoto