Hmm, not in real life. I can write a script that parses the blockchain and keeps track of the transactions. How many people/authorities can do that with FIAT?

Hmm, not in real life. I can write a script that parses the blockchain and keeps track of the transactions. How many people/authorities can do that with FIAT? Not to count the impossibility of actually tracking down FIAT that has not been used by a bank or authority that CAN actually control the unique number :-) So in case 1 it's very easy to do, in second case is almost impossible outside very well defined scenarios (police trying to frame drug dealers, etc.)