Pardon the generalization: I don't mean to attack 23-year-olds specifically. Nor do I believe there are no young people capable of managing a business's social-media responsibilities.
I am, however, trying to make a point: Just because you don't understand social media doesn't mean you should forfeit all common sense and hire your niece, nephew, or any other recent college grad (say, your best friend's sister-in-law's kid) because "they're really good on Facebook."
If your business targets the young and hip, most definitely look to a recent grad or young social-media nerd to help your business. But don't assume, either, that you need to hire someone young to manage your social media "just because."