Do users need to authenticate to access their preferences page?

General Discussion
1

I’ve read about pref pages, which would be very interesting for me to use, as users could choose for different interests via this page. Right now i think the interests would be set as different segments, the user can enable/disable.

Is this possible?
Is it possible for a user to opt-in into a segment via the prefpage?
Or is it only meant to opt-out (re-opt-in) once you was put there by a campaign or the admin?
Do users need to register to be able to get to the prefpage?
How is the page secured if it was accessible without login?

2

If the segment is marked visible in preference page .

It’s generally accessible by unsubscribe link, and it’s a tokenized link. Accessible by anyone with the link.