Trolls could send you mixed Bitcoins to taint your entire stash. I suppose there could be a protocol for refunding the trolls to clear your name, so it's probab

Trolls could send you mixed Bitcoins to taint your entire stash. I suppose there could be a protocol for refunding the trolls to clear your name, so it's probably not a big deal. If you operate an MMO or other game where people can buy virtual currency, then the game acts as a "bank" that does periodic settlement transactions with the outside world. Lots of people are thinking about off-chain transactions in this manner, and it seems like you'd be hurting its utility if you couldn't. Then again, games usually don't let you take money out because then they could be used for money laundering. Exchanges have significant Bitcoin reserves and their employees are highly invested in Bitcoin. If they collectively blacklist other people's coins, they stand to benefit. So there's a conflict of interest. If Exchanges put a system in place to blacklist certain undesirables, what stops the feds from whispering into their ear, "You should add these porn and gun sites to your list. They're not illegal, but it'd be a shame if we found something else to investigate you for." https://en.wikipedia.org/wiki/Operation_Choke_Point https://en.wikipedia.org/wiki/Operation_Choke_Point The policy would increase the value of newly mined Bitcoins, which would further centralize mining in Iceland and China, which have cheap(or subsidized) electricity. Miners would have to reject these transactions, because otherwise it would end up in the transaction fee and in their account. Miners deal with a larger tree than just the main path, and it might be computationally expensive to calculate it for each transaction. If you exempt transaction fees, then pools stand to make a huge profit by cleaning mixed coins and would probably find a way to do it. If the miners, exchanges, users don't use exactly the same algorithm and blacklist at all times, then there's a possibility to profit by e.g. scamming a Bitcoin gambling site using newly-tainted coins. I feel like there's already enough ways to lose your hat from one subtle mistake with cryptocurrency, and we don't need any more.