Check the article link below for pro/con analysis by Simson Garfinkel
Facebook's identity system might very well supply something that VeriSign, Microsoft, Yahoo, and Google have all struggled to offer: a single "driver's license" for the Internet. (This leaves aside the question of whether it's a good thing for one company to hold such a position of power.)
A unique combination of factors makes Facebook well suited to being the repository for people's identities on the Internet. Unlike many popular websites, it requires users to register and log in. And Facebook's terms of service require that "users provide their real names and information"—indeed, Facebook has terminated accounts that were created with seemingly fake names or for fictional characters. Since Facebook users invest their accounts with a tremendous amount of durable personal content—including photographs, contact information, and connections to their social network—they are likely to keep a long-term relationship with the site.