You, sir, would make an excellent UX specialist for Microsoft.
It's always difficult to recognize compliments from sarcams:-) But I'm an optimist (I always think the glass is half empty but at least it isn't totally empty) so I'll interpret it as a compliment and I'll thank you :-)
I think perhaps features like this would be best left to alternative Bitcoin clients to implement. The official client should be as secure as reasonably possible.
This wouldn't make it "less secure". It would make it "optionally less anonymous". Technically it would make it MORE secure (because you would have less chances to lose money because you don't have a newer backup). There is a sliding scale security<->anonymity. Some persons want one, some want the other. I think Joe Six-pack would prefer not to lose money if given the choice, while the Joe-Everyone-Spies-Me would prefer to be totally anonymous. And then, if it's an option in a menu, when you need a more anonymous transaction (and it probably isn't truly more anonymous, because the money can still be tracked if you don't know what you are doing) you can still reactivate the "advanced" mode.
Ah... And why isn't wallet.dat an xml? It would be easier to edit it "by hand" in this way (for example to split/merge wallets).
