Sometimes people send bitcoins in order to make pretty sounds on
http://www.listentobitcoin.com/The minute you think its more than that, you expose yourself as the conniving one. They're called wallets for a reason... If I choose to move money from my black leather wallet to my blue suede wallet I'm free to do so (and subsequently move it back).
If someone chooses to move coins from one wallet to another, now... all of a sudden because the balance of wallets is public, you're entitled to more information?
---
Edit to add more information: Bitcoin has such a great quantity of available wallet addresses that you can perform transactions and throw away the wallets that you started with.
I pay with my black leather wallet.
I put my coins into my brown leather wallet as the other individual (A) puts their coins in their wallet.
I pay with my blue suede wallet.
I put my coins into my green frogskin wallet as the other individual (B) puts their coins in their wallet.
... repeat ad nauseum.
(This is also a standard feature of some bitcoin wallet programs. What purpose does it serve to always return to the same wallet? Its a concept stuck in the material realm.)