This question is geared for a line of business application someone would pay for, not a general public facing website. Is it better to redirect for authentication/re-authentication or show a pop-up? ...
Why would you, for a local authentication site, have usernames, instead of using e-mail address to login?
In websites where authentication is local, or mixed local and remote (e.g. OpenID), I still often see the question for a username. I can very well understand this in the case of twitter, where the ...
from a usability perspective only (not security) what do users find more comfortable A site with it's own login page (need to sign up but then easier to login) or a site with remote authentication ...