I've hacked the code to force a user to login, but being able to simply toggle this would be great. With forced user login turned on, then two features I'd like to see are:
1) Tag pictures with what users are in them (choose from drop-down / checkbox / whatever, etc)
2) Comments are automatically tagged with username (and email, website, etc) instead of having to type it in every time.
Comments
if you include `` in your comment form (all the zenphoto themes do this) then the user will have to enter his information only once.