Are online exchange wallets effectively bitcoin mixers?
Any wallet a Joe Bitcoiner has with an online exchange is a bitcoin mixer, right? Bitcoin hits the wallet address, record of the amount owed on that wallet is made, and then the Bitcoin is routed to the online exchanges master wallet for facilitating transactions. At this point Joe Bitcoiner's funds are mixed with everyone else's.
If someone were to follow the transaction trail on the blockchain they'd get lost in the process and never be able to link the incoming funds for Joe Bitcoiner with where those funds are held or further spent.
I suppose the only thing that makes this untrue is if the online exchange exposes the transaction records for Joe Bitcoiner's account - yes? (Unless Joe Bitcoiner is using https://torwallet.com/)