[alanfalcon]

How do you effectively blacklist an address when you can just generate a new one? Treat it like a one time pad; unless the government is sending out these black lists in real time (but even then...)

[quickthrower2]

You could blacklist the originated address and then algorithmically ban any addresses they have spent money to, recursively.

If your address is banned by being downstream, you have to do an in person ID check or whatever and explain where you got the coins from.

Edit:

I have always wondered about the fungability of bitcoin. The case above would mean you have some 'hot' bitcoins that are probably worth less than market value. Someone may buy them with freshly mined ones for an exchange rate < 1.

Another scenario is really old bitcoins from 2010. Would they be worth more to 'collectors' if you can get a nice lineage.

[tCfD]

Old transaction outputs will be worth more at very least because future forks will try to legitimize their distribution as being, at least, no worse than Bitcoin by cloning its blockchain. Though that tactic may have run its course by now, if you already hold old outputs you probably aren't inclined to move them anyway, especially if they have the potential to spawn new, disposable offspring.

[Frogolocalypse]

Bitcoin is just a chain of transactions. This address to this address to this address to this address, right back to the block it was created in. It is not terribly difficult to validate whether the payment you're currently looking at existed as bitcoin in that address at some point or another. Like I said though, even the ability of that is likely to be undermined over the next 3-4 years.