Personally, I don't think the Facebook login plugin is ready for prime time inclusion into the Q2A distribution.
Some of the more obvious issues:
1. It requires php5-curl to be installed. Judging by my experience (and the large number of "Facebook Login Plugin module not working" questions on here), most installations don't have this installed by default. It takes a bit of digging around to find this is a problem. The module should either test and indicate this to the user, or at least have a mention of this somewhere easily visible. Not yet the case. (HINT: sudo apt-get install php5-curl)
2. Even with php5-curl installed, I am still having problems with it, and it feels like all of the possible use cases for this module have not been tested. Some more obvious things not working:
- I can log-in using Facebook login through my Q2A website if I am logged out of Facebook, but not if I'm already logged into Facebook.
- Duplicate registration is poorly handled, if at all. Users already registered into the Q2A website who try to login via Facebook will face a problem that's not handled well.
- Issues about what exactly happens when people log out (see here: http://www.question2answer.org/qa/24877/facebook-log-in-functionality
- Spontaneous redirects to blank screens (can't provide more info as they are quite random)
Maybe it's just me - I get scared editing PHP code, but all of the other plugins included in the distribution just work by doing web config. Facebook login seems a long way from doing so. Clearly the Q2A developers are working on a whole lot of stuff (and doing an amazing job), so I'm not having a bitch and whine, I just think less people will spend time trying to get this to work and failing if we acknowledge the fact it's not quite ready for prime time.
So please +1 this if you've tried to use Facebook login and failed.