If your identity is known at the exchange, then it doesn't matter what denominations you send the coins in, they can be linked to you. Zerocoin looks very promising, because 1. It offers true anonymity by design, where it is possible for you to be the only person in the world who knows that 2 txns / coins are linked. Current mixing services offer security by policy, where they promise to delete the accounting details linking coins going in and coins coming out of their wallets. 2. It will be cheap. Currently, anonymizing coins can take anywhere from 1.5% to over 10% in overhead fees. Presumably, because Zerocoin transactions are larger than normal Bitcoin transactions, miners will demand a higher fee, but it might be something like .005 BTC instead of the standard .0005 BTC. So you will be able to anonymize any amount of money for 50 cents. For a detailed explanation of Zerocoin, see this thread: http://dkn255hz262ypmii.onion/index.php?topic=152682.msg1057894#msg1057894