I would like to give my users the options to log in with other systems - not just Facebook. I would also choose Google, Twitter and Linkedin. It has to be properly designed though - users should be forced to enter any "required fields" in the join form. The RPX integrating here apparently is no longer supported - another thing here I wasted months on that never worked properly. It would also be quite expensive if a site ever got to be successful.

This is all academic, however, see more since the software has so many serious problems that it is almost impossible to get it working in the real world.