When it comes the time to add OAuth support to your Symfony2 project, and allow your users to login using their accounts of Facebook, Google, Twitter, Linkedin, etc., it really makes sense to use some of those great third-party bundles that already solve this problem.
One of these bundles is the HWIOAuthBundle. This is a great bundle that allows you very easily to add support for authenticating users via OAuth1.0a or OAuth2 in Symfony2, handling more than 20 providers.
But as today, there is only a little problem… documentation is not as detailed as some may want. This is only my very small contribution after fighting to make it work.