Generally, you just need to unpublish the JFBCSystem plugin. That plugin is what enables all other features on the site, like authentication, channel posting, social widgets. Without it published, the login buttons will not show either, so you shouldn't even have any 'dangling' features that look like they should work when clicked... it really will be a site without JFBConnect.
With that said, if you have some modules or other items configured, you may see something here or there, but disabling the JFBCSystem plugin is the easiest switch to flip to turn off 99% of JFBConnect features.
I hope that helps, but if you need anything else, just let me know.
Thanks,
Alex