Personally, I prefer the way Twitter and Dropbox ask me to enter my email and password (once). The submission of a user name and real name are needed for applic

Personally, I prefer the way Twitter and Dropbox ask me to enter my email and password (once). The submission of a user name and real name are needed for application specific setup. I suspect that most users will use standard passwords and don't change or make these passwords more secure only because you ask for them twice. In general, I would say that each additional input box will scare away more users.