>"So if you get a warrant to search your hard drive for something, you are compelled to give them the password just like you are compelled to let them into your house if they have a warrant to search for something like drugs or guns or counterfeit plush toys."

You might also be missing something about TrueCrypt: plausible deniability. You can have different passphrases that unlock different things. You could provide them with a passphrase the only unlocks innocent documents when really you have CP stored using a DIFFERENT pass phrase -- any this would stand up to any cryptographical analysis -- they simply cannot PROVE that the CP exists or even that more encrypted data exists.

The analogy to a key isn't quite valid here; it's more like the doors in that hallway in the matrix. If you use key A in the door, you will get content A. However, you can use a different key, open the door, and it'll go somewhere else entirely. Also, if you rip the door off the wall, there is just the wall behind it. Crazy stuff, that.