OAuth registration and login (Facebook, Google ..)
My installation is intented to public. But people do not like to register. It is boring, it takes time, you need to remember zillions of passwords and it is not safe (databases are bing cracked). The solution was provided by openid first and its successor OAuth that is widely available. People can delegate authentication to OAuth providers like Google, Facebook, Twitter, LinkedIn and many others. It is very fast, convinient and reasonably secure.
Because you already have openid, the implementation will not be such difficult. The concept is the same. Thank you for consideration.