This relates to my idea from Alt-Coin (ie. spam board):
TrustCoins:
https://bitcointalk.org/index.php?topic=220513.0I didn't think the idea belonged here because it is a totally different model than mining and clearly bitcoin could not ever change over to it exclusively, but...
I'm thinking it could be partially implemented as a "soft" addition to bitcoin protocol (ie. for informational purposes but not honored) as a secondary option against future attacks. Ie. if bitcoin was to at least build a network of trusted miners and each miner (pool) who adds blocks to the chain was to also add their signature to that block, it could potentially be used to blacklist a future attack and to select the chain of the most blocks with trusted signatures.