There are some applications that require anonymous users to login, even if they are configured as "Public (no login required)". The ones that I found:
Audit Calendar People Individual profiles require login
Owners Tokens Facts Conduit UIExamples XHProf
Maybe some cases do deserve a login (like the obvious "Settings") , but at least as a new anonymous user browsing Phabricator it feels random / buggy. Accessing to these applications as registered user, I don't see any reasoning for requiring login in most cases.
Just for the record, this is the original task in our project: http://fab.wmflabs.org/T115
PS: This is my first bug reported here! As a Bugzilla user I'm not even sure whether it is fine to add so many projects. Let me know if you prefer separate tasks, otherwise we can edit the descriptions striking out the cases resolved.