Whose talking about laundering money? I am just talking about securing your bitcoins.
Because the bad guy can see the history of transactions of your "everyday" wallet. If there something suspicious, like big transfers for only one address, it's a problem. You can manually "laundry" your money generating new addresses in every transaction at your "savings" wallet. Make it little chunks at a time, with broken numbers. (Just a little paranoid right now.)
In future versions of the client, Bitcoin should look more like an user-friendly password-protected crypto-currency with plausible-deniability of it's existence (multiple hidden volumes). OR kids in school should learn how to protect and secure a digital file right now.
It's very hard to be your own bank, but i'm loving every minute of it.
Yes, an attacker could see that you transfered money from one account (the "rich" one) to the day to day account, so what? It would be extremelly difficult for him to attack you just in the precise moment you fire up your computer with the USB and the minute you need to transfer funds to your day to day account to use them. Specially since he/she has no idea when are you going to do it and it could be months or years for you to use that USB. And then he would have to detect the new computer, find out the operating system and hack it in a few minutes. And if you are very paranoic you could to it in your neightbour computer that has a different internet conexion.
There is no system 100% secure, not even the network at the Pentagon, but the odds of someone fucking you if you do this are very very low.