personal sites

Hello there!
If you want to give a user total control over a site (his/her site, area, or whatever you want to call it), what should be better? Creating a group for each user, as in drupal Groups, or creating a multisite installation?

When I say "total control" I mean everything: Blogs, polls, newsletters, have a fan´s group (not buudies, I mean actual users that are created just to enter his/her personal site).

Would multiple sites installations become a huge monster, that no server could manage?

What are your thoughts?

Rosamunda