There are many ways to make people register themselves, for example the Safe Route or the Doodle Way. But on many sites, you can just login using Google or Facebook or Twitter, beyond other means, nowadays. This is the Driver’s License approach, where you make users login into one of those services, and the service tells you who that is and that he’s logged in.
This way, you can more or less identify users. This has a positive result for you and the user, as you don’t have to store their password – and you don’t have to deal with password hackers that hack sites like Gawker and steal the users passwords. On the other hand, you can’t adress those customers directly as you also don’t know their e-mail adress necessarily – and this is why this method is often not used too much. Being dependant on the service is also a problem of course – what happens when Google is down, for example? :-)
For users, this way of registration is great. They can login easily, and don’t have to invent a new username or password for your site. You’ve just NOT complicated and cluttered the internet even more.