At the very least, I've avoided using online wallet services after reading about btc thefts. So the argument about keeping those savings accounts on physical media and physically locked in a safe is not a bad one to make.
Maybe it would be smart to have a locked safe, but nothing in there. When the thief comes they steal your whole safe and take it with them only to find it is empty once he/she cracks it open at home.
Then you as a smart person has a usb stick somewhere that nobody else would even dream of where it could be.
I don't say you should use this technique, because if everybody used it then the thief would not look for the safe, but though again you could be fooling around and then have it in the safe, making the thief look stupid(while he/she avoids searching the safe).
What about that combined key thing, where for example your key from your cell phone gets combined with the key from your computer bitcoin client key into one whole that signs important transactions?
I think it has been implemented in bitcoind, but how to use it in an easy to understand way? I don't know. Isn't that called "Multisignature transactions"