There's no question of whether or not social games are big money, but breaking down the user demographic has been a long-time effort of many studios and research firms. Arkadium, a game development studio, has provided one of the latest dissections of which types of social gamers spend what.
Since the explosion of mobile gaming in the last half-decade or so, it's developed an image as a "quick fix" medium full of bite-sized experiences meant to pass the time more than occupy it intelligently. And while I'd be out of a job if the opposite weren't also true, a recent survey by mobile game portal MocoSpace seems to prove that - as with all things - stereotypes exist for a reason.