The next time you log on to your facebook site, look at the ads on the right hand side.
"What ads you say?"
Right. But just for fun have a look. Those ads are supposed to be matched to your profile. They are targeting you. In my case, last time I looked, only 1 of the 4 ads listed applied to me as I had been searching online for glasses. The other 3 not even close.
So before you jump all in with your advertising on social media sites and forego your traditional media, remember, Facebook is a social medium not an advertising site.