Almost all countries follow the US imposed sanctions against Iran. If you don't it will be very hard to do business with anyone in the US. Here is an example of a bank from my country being fined by US regulators for allowing transactions to Iran (and Cuba):
https://www.reuters.com/article/us-ing-sanctions-idUSBRE85B1...
> A two-year criminal probe was conducted jointly between the U.S. Department of Justice and the office of Manhattan District Attorney Cyrus Vance. The Treasury Department’s Office of Foreign Assets Control conducted its own investigation.
Companies follow those sanctions because they don't want to be slapped by US regulators (they don't have to pay the fine, but that means losing access to the US banking system). Not many western countries besides the US have problems with Iran (as opposed to other middle eastern countries).
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As to your point: everyone creating a blacklist is a big hot potato game. If you're not on top of the latest hacks and get some bitcoin that were stolen you'll be at a loss. This would defeat Bitcoin's fungability and defeat it's purpose as a currency.
The same happen with counterfeit money, yet here we are, still using it everywhere.
In most case, if it's physical, you can catch it before it get send. If it's digital, you can cut access. No big deal.
Go see any big Ebay seller and find one that didn't lost any money from a scammer.
We are talking about blacklist that would make a stolen bitcoin, no longer a real bitcoin and thus be at lost. If you consider it still a real bitcoin, how can you consider it a loss? If it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck. If it doesn't... it's probably not...
You talk about being on top of the latest hacks... isn't the same as being on top of the latest counterfeited money?
And in my second paragraph, I make exactly that point:
make it more useful by saying "I don't trade with anyone who doesn't also share my same blacklist"
A blacklist like you suggest has been tried and shot down many times, for example: https://bitcointalk.org/index.php?topic=333824.0
Not necessarily. Each person could create their own blacklist, and just not trade with anyone who is using coins on it. Granted, that requires personal integrity. But it's a bit like saying "I don't do business with Iran." Some countries do, others don't.
If you are skeptical of the personal integrity component (on the part of others) you could make it more useful by saying "I don't trade with anyone who doesn't also share my same blacklist"