The light version of this pattern is the shopping cart of an e-commerce site, where the user can accumulate relevant products in a cart and then in turn register an account if he or she chooses to make a purchase.
In the heavier version of this pattern, an anonymous user account is immediately created for the user – full with an auto-generated database ID and a complimenting cookie with the account’s ID that will ensure that the user’s details and the information he or she has entered will be remembered upon the next visit. With appropriate intervals, inactive anonymous accounts are cleared from the database in order to not clutter it up.
As the user interacts with the system, data is accumulated to the account. While some data might not be shown to the user other kinds of data will. It is the latter kind of data that in turn will make the user register – the visible evidence that the user has invested energy into using the system. A smart way to gather such data is to expose holes of data that the user can populate.
Two such holes are the username and password: the two bits of information that will allow the user to log into his account from more than one computer.
For this pattern to work, you need to provide the users with an incentive to give you the registration data you are looking for. You need to provide a worthwhile service to your users for them to give you their data back in return. You want to use classic Carrot and stick motivation – and just as important: communicate the benefit you are providing. If the registration data you are looking for with the user is sensitive, you must be able to assure your users that their data will be safe and secure.
At penzy.com, you don't have to create an account to try out their product. The application lets you play around before you decide to save your work.
Geni.com let's you start immediately without registering for an account first. It lowers the barriers of entry for the user to start exploring and be motivated to actually signing up.
Slide.com lets you play around with their software before you decide to sign up.
Scapblog.com uses the lazy registration pattern to lure its users into signup. It postpones signup until the user has put enough time and effort into the web application, that not signing up for an account would make him or her loose work put into the application.