If you really want to get rid of sign up forms, having a large scale trusted and secure central repository for unique IDs/logins and 'commonly requested' information would eliminate the need for many sign up forms. The majority of web based applications, services, etc. ask you for the same information repeatedly without any actual need or use for the information as a value add in the functionality of the application. Why is that? Why hasn't this been done/worked in the past?