If you don't even know someone in your social network well enough to know whether they'd be qualified for a particular job, then you probably shouldn't be referring them to your employer, since you have no way of assessing how good they are at what they do. Passing someone's resume along to your employer is an implicit endorsement of that person, and if they end up being a waste of the company's time, your own credibility will suffer. Not to mention that when you later refer a really good person, they may get ignored due your past history of recommending unqualified candidates, and you'll miss out on referral bonuses.