Just checked it out. Here are the take home points: * the registration link is titled “sign up” (40%) and placed in the right upper corner, * sign-up fo

Just checked it out. Here are the take home points: * the registration link is titled “sign up” (40%) and placed in the right upper corner, * sign-up forms have a simplified layout to avoid distractions for users (61%), * sign-up forms are one-page-forms (93%), * sign up forms attract visitors by explaining the benefits of registration (41%), * titles of the input fields are highlighted bold (62%) * no trend in the label alignment can be identified, * designers tend to use few mandatory fields, * designers tend to use few optional fields, * vertically arranged fields are preferred to horizontally arranged fields (86%). So, it seems, from this data, that 3-5 fields are OK, including full name and username.