You would have to get 51% of miners to cooperate for a blacklist to work completely. I don't think that is likely to happen.
Put centralization in the protocol? With a link to a single entity that can render all coins on an address useless? As you've said that is definitely never going to happen: First the devs / foundation will never get convinced this is a good idea, after that no miner / node I know of would ever update to such a version, if it does a fork / altcoin is probably going to take over.
Perhaps you overlooked the fact that you would still have to send the bitcoins from the blacklisted address to the new address. A blacklist would prevent that.
It appears to me that at least half of the discussion is about a list not enforced by the network but by the community (on top of Bitcoin itself).
- If a private key gets stolen in almost all cases the owner will find out after the coins have left the wallet, if sent directly offchain (like to Mt. Gox for example) are you going to blacklist the addresses of Mt. Gox?
- If this list is central in any way every goverment / legal body can attack the list, or poison it with extreme ease. If it isn't it is going to be attacked by basically everyone else because it is the power to control the whole monetary system.
- And if you have a wallet that has stolen BTC from a blacklisted address 10 transactions back, are you allowed to trade? Hell I can even steal BTC, send them to random people to have them blacklisted ?
- if I don't know about the list / don't got the most recent version / etc. and I meet up with someone and buy some Bitcoin I can't use them at all?
- Good luck finding a way on determining who scammed who in basically the whole scammer accusation forum.
- What if you later find out about coins that were stolen x time ago but are now distributed across the whole network?
This would only work when you get all exchange parties on board (including parties like silkroad), somehow deal with mixers / exchanges or other parties that don't want to be obey to a blacklist. After that you have to make sure the database won't get hacked / lobbyd / controlled / spoofed by governments (or IPSs).
And if you find a way to deal with all these problems you just introduced centralization to Bitcoin?
So it's an extremely bad idea and it can never be implemented fairly any way.EDIT: I would suggest instead of a blacklist that if you are going to trade with anonymous people on the internet and prevent scams from happening in the first place, you use a trusting system like bitcoin-otc. And if your bitcoins got stolen you should have been more careful (it may be hard, but that is the way it is right now).