Kilkenny

The "delete all previous versions" of a file would be a really important utility. The example mentioned previously of wanting to expunge all traces of a sensitive file is a good one, but the first example that came to my mind while watching the video was malware removal.

ie. lets say you update your AV/AS software, so now it catches a lot of stuff that was missed before & now it finds that you have installed malware... the AV software will have to be able to remove the current files as well as removing any/all previous versions of them to ensure a clean system (and that the system won't get re-infected by the user restoring previous versions of evil files).

I also wonder if it's possible for advanced malware to inject files into previous versions in order to hide them for later re-activation.

I don't really think that those two guys really understand how user accounts work in the mac. Pretending that the mac has a sinple log in/log out that puts you in an administrator account with full privileges is just a big lie to the face of the camera.

That's not what they said, they said it used a "Lock/UnLock" model where your default account type was "administrator", but in the same way a standard Vista admin works - ie. you run as a regular user most of the time & are prompted for elevations when running changes that require Admin access.