I'm not sure I understand your question- would you mind elaborating a little?
To clarify Adobe Social is not a social media platform itself, but a tool to manage all of your social media properties in one place. Using Adobe Social can schedule posts, moderate, get analytics, etc. from your existing Facebook pages, Twitter accounts, G+ pages, etc.. So yes, all existing Facebook fan's comments and Twitter posts will be pulled into Social when those existing properties are added to the suite, but those fans will not be users. Any users of Adobe Social for your account will need to be set up individually. These users are usually internal to the company who's account it is- Community Managers, Support, Analysts, Marketers, etc..