Not required at all. Though we have profile integration plugins for K2, Agora, Kunena, JomSocial, and Community Builder which lets you import the avatar and profile into those systems, there is absolutely no requirement to have them.
Without profile integration, the core JFBConnect component allows for single-sign on, import of name and email address into the standard Joomla user table, and use of all the social modules (invite, like, fan, etc). Until we added Agora integration (earlier this month), sourcecoast.com used JFBConnect without any profile integration.
Hope that answers your question. No 'duh' questions here, JFBConnect has a ton of features, so it's not uncommon to be unsure of exactly what is or isn't required.