A feature which DevExpress has recently released into their library is the oAuth integration library. This allows for Facebook, LinkedIn and popular oAuth login methods to connect to your XAF or ASP.NET website. A nice feature of this tool is the automation of the login process, and seemless integration into websites.
This login method is a token based login, which was not a popular method until it was adopted by media giants such as Google and Facebook.There are a lot of good sample websites on how to use oAuth if you were to write your own integration library:
I would also recommend reading the third part in the DevExpress blog regarding setting up an oAuth website while using their controls. It is a great read, and helps any developer get up and going with this technology in a few simple steps: