[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.