Alea,
It's not about back doors although I'm sure that capability exists in some technology.
With the TPM is about the keys for the encryption and where they are stored.
If they are stored on the device in software they are easily hackable. If they are in a TPM CHIP it takes more effort. If they are held in a HSM they are really difficult to get at but not impossible.
The best system is to have the encryption keys never reside on the device.
Even with that I'm sure there is a way that the brightest of the bright will find a way.
Raise the bar and make it so the crook does not just walk right through the front door.
That's what the industry is doing and look at the new business models being created, some quickly and some not so quickly.