A question about registering with your facebook account on other sites?

[MVin]

If I add this option on my site, and if people register to my site with their facebook account, does it suppose they have an account on my site. What's the difference with "traditional registering"? Just speed of registering? If someone closes his facebook account, is it automatically closed on my site(the account)? Can facebook interfere in this process like disabling registering with their account. Thank you for your answers.

[Astano]

When someone registers with facebook you just make an application and then request certain pieces of information from facebook, you then populate this information on your database and your all done. If someone removes your application you can set-up a script to remove them from your site but it's likely they'll use your application to register to your website then remove the application after as it's no longer needed! This just speeds up the registration process and saves the user some effort!

Process Flow

User registers with facebook
User then accepts your application
You save the user information to your database
You then redirect the user to a registration form
The user can then add a password and any other information you need
You now let the user login
The user can delete your application from there account if they so wish