Whether or not it's the same thing, it uses the same mechanics. You can link the output of one transaction to the input of the next, and construct a chain of tr

Whether or not it's the same thing, it uses the same mechanics. You can link the output of one transaction to the input of the next, and construct a chain of transactions that says "This 0.125 BTC transaction uses bitcoins that were originally stolen from MtGox / bitcoins that were originally in the pile designated as marking ownership of my shares of stock". The question is whether that's a meaningful thing to measure. If you have bitcoins that are more valuable than normal, because they're shares of stock, then you'll make sure they're not mixed with "normal" coins. That's the idea of the Coloured Coins project. But if you have bitcoins that are less valuable than normal, because they're stolen goods, then you'll try hard to disguise that fact. You'll immediately spend them on goods or currency, or deposit them into a Coinbase account and then withdraw them later (so you get different coins back), or just throw them into a mixer with the other coins that need to be laundered. The person who ends up holding the tainted coins could be perfectly honest, and have acquired them from a perfectly honest source, who in turn acquired them from a perfectly honest source. Is it fair to tell them that their money is suddenly worthless, when they had no way of knowing anything was wrong?