Newbie question. AFAIK, each US banknote has a unique serial number. Is the same true for bitcoin? Does each bitcoin have a unique identifier, regardless who owns it? Does each satoshi have a unique identifier?
The movement can be traced due to transparent blockchain.
Lets say FBI puts some addresses that were used in conjunction with illegal activities, now every coin from this address will be traced by them and who ever uses this coins may have some trouble explaining how he got into possession.
Many people had their accounts banned on exchanges due to this "tainted" coins.