I have never liked companies to access my Facebook pages when I join a site. I would rather enter my email address, password and information to join the site. The site will send me an activation link that I can save in my folders for reference. This makes it easier to find out what sites I've joined and what sites have my information. If you join with FB you don't have any records from the site and in the end, you can forget what site you actually joined. I think it is best to add my own information to the site and not use the automatic login information from FB or Google.