Interest in per-user homepage categories/taxonomy

At the institution where I work, we are considering a couple of different ways to allowing users to have their own set of personal pages (which others cannot modify), with navigation that can be managed easily by them.

One approach is to use CCK to create a set of pre-defined pages that they can use. This makes it easy for them to set up, but lacks in flexibility.

The other approach is the one I'd like to get people's opinion of:

1. Using the category module, administrators would create a default vocabulary for all users
2. When a new user account is created, they would get a copy of this vocabulary; permissions would be set on this vocab such that only they can edit content created with it, but everyone can view the content
3. Users would optionally (at the admin's choosing) be able to edit the vocabulary

I believe this could be done using modifications to just the category module. What do people think? Is there anything I'm missing? Before I start coding this, has anyone else already done something similar?