This is the crux of the problem. Physical (and network) access can always break any security because you have a million vectors of attack - physical hardware, software, etc.. . And how secure is your laptop when its in your possession? As laptops become smaller (i.e. netbooks) they'll be as easily stolen as one's wallet.

Frankly, most people's data is really not that important and the cinderblock attack is what truecrypt and similar crypto systems prevent. Every time you see a news item about "a million social security numbers have been compromised " - its always due to the cinderblock attack.

The "only" way to secure your data is to put your computer it in a vault (unplugged from AC outlet and no network access) with multiple physical security and surrounded by people with guns. If your data is that important and you can afford this sort of security...then the evil maid attack is irrelevant.