I was talking the first option, where Tivo's programs are guaranteed to be authorized but users can authorize more for their programs.

However after a while a third party will produce something useful, and every user who wants to use their software will have to authorize that third party's keys. If you want to use stuff from 3 people, you need 3 keys.

Before long users and developers managing this will decide that it is easier to just share a private key among developers. Then users only have to authorize third party software once, and they get lots of software.

So the first option, DRM but users can adjust who has permission, effectively becomes no DRM in the end.

Cheers,
Ben