Thats the main problem.
Your "addresses" in my view are accounts with just one turnover only.
The question is: why only one?
To hide transfers and balances this way cannot be very successful, since all public.
But in this case an (encrypted) field "reason of tx" is definitely necessary for commercial usage.
A merchant and his computers not able to know WHO payed him for WHAT cannot use BTC.
Again you stick to the classic way of bank accounts, and only accepting this strict convention.
Let me try to rephrase:
The "problem" we face is: person P buys a thing "T" from merchant M, and P initiates the payment to M.
Now M needs to know that P paid for T when the payment arrives.
Traditional solution: M has a known bank account B, P can transfer the money to this account B. But because everybody else buying from M pays to this same account, M needs additional data. As the bank account of P is not known to M, something like a "reason of tx" field is necessary to relay the information "I'm P buying T".
Bitcoin solution: When M and P make the deal, M gives P a bitcoin address A. P pays the necessary bitcoins to this address A.
DONE. No further information is needed, as this bitcoin address is unique (only used once, exactly for the reason of P buying T).
An elegant solution that covers your problem of "merchant needs to be able to know WHO payed for WHAT", and at the same time keeping some privacy (nobody can link address A to M, except P).