>I think the correct response is asking how they would get back their money if cash was stolen from their house.
But stealing Bitcoins doesn't require physical access to your property. That seems like a pretty big distinction to me.
Edit: And if Bitcoins are like cash, why should I bother using them? I already have cash (that I don't use very often) available to me readily. And since I get paid in dollars, what advantage do I have to use a separate currency solely for rare and unimportant transactions?
Actually, yes, stealing bitcoins will increasingly require physical access as technologies for storing them offline evolve: brainwallet, paper wallet, credit-card sized electronic bitcoin wallets (at least 2 in development).
I personally think the latter is what will propulse mainstream adoption of Bitcoin, as it will make it impossible for inexperienced users to leave unsecure bitcoins on their computers.