When a user is unfamiliar with an option provided by a system, they may wish to see what facilities it offers or what inputs will be required, without either indicating or making a commitment to using the facility.
This situation is similar to someone browsing in a shop. An over assertive shop-keeper, who rushes to enquire what is required, may prevent the customer browsing as they are intimidated by the demand to commit themselves up front. Thus, a Web site that demands the visitor identify themselves before proceeding, runs the risk of visitors backing off in fright rather than finding a service that they may use.
This also applies to completing a form. Entering a personal identification — an email address, or a user ID feels like a signature, and it is unwise to sign anything before reading the small print! The user may not know at what point the system takes the details that they have entered. If a form overflows the screen, they may not be sure that they either wish to, or have the information to hand, to answer all of the questions. Whilst it is possible to scroll up and down the form to inspect it fully, users may not be aware of that possibility. Full inspection of the "contract" is not possible if the form is split over several pages.
Therefore:
Where possible, make the entire contents of a contractually obligating input form visible on one screen, and always make the entry of personal identification details the last items.
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