It doesn't seem likely that spam registrations would come from the social login features of SCLogin/JFBConnect, which leaves only normal Joomla user registration. SCLogin actually does not actually perform the registration/creation of the user, but instead just redirects to the standard Joomla user component. You should be able to use any spam prevention measures that work with the Joomla core and already built-in Joomla features such as reCaptcha. I don't think you'd see a difference in the amount of spam registrations from using our SCLogin module versus the standard Joomla login module.
-Melissa
How to stop spam
