Amit Singh has a fascinating technical article on Apple's use, non-use, and ultimate abandonment of the Trusted Platform Module (TPM). This is the core of the Trusted Computing initiative, a chip that can, depending on implementation, be used to lock you out of reading your own data on "unauthorized" applications, to allow network service providers to discriminate against users of alternative software (e.g., "You're using Firefox — go get Explorer and come back") and enforce DRM — but also allow you to better secure your own data (you can do the latter without enabling the former, too).
With the release of its Intel notebooks, Apple became the only manufacturer of Trusted Platform Module systems that didn't disclose the details of its implementation, something that lots of users (myself included) found alarming. It was this that precipitated my decision to move from Mac OS X to Ubuntu on a ThinkPad.
Now, Singh reports that Apple has dropped the TPM from its motherboard designs, with the new MacPros. Singh had created a free software driver for the TPM under OS X that allowed users to exploit its privacy features.
This is good news for Mac owners, on balance. Of course, the best outcome would be for Apple to leave in the TPM, but to also publicly promise to eschew all anti-user features in its drivers, so that Singh's users could continue to enjoy privacy benefits without concern over the potential dangers of the TPM.
(via Hack the Planet0