[qiqitori]

By design, every single transaction is tracked. Otherwise you'd have a hard time proving that you have any BTC at all. In fact, the miners implicitly verify that all purchases are tracked, by doing something like the following every "block":

new_hash = hash(previous_hash . all_new_transactions . random_number)

You won't immediately know if A, B, C, and D are all the same person, but you can look at what has happened at those addresses (or previous addresses) in the past, and (eventually) what happens in the future, and draw conclusions from that. If you use a new address for every transaction, and never merge your money, you may be able to obfuscate the flow for a while, but you have to make sure you don't leave any patterns in the timestamps, and make sure you generally know what you're doing. Any mistake could mean that people know it's you. Moreover, money is generally used for 'offline' things eventually. You may purchase something from a completely normal person who doesn't obfuscate his transfers at all, and then get outed when the police ask that guy who they got those suspicious coins from.