Being able to target ads well doesn't do you any good if you don't have the ad inventory to make use of that advantage. That's Facebook's problem: their users a

Being able to target ads well doesn't do you any good if you don't have the ad inventory to make use of that advantage. That's Facebook's problem: their users aren't apt to click on ads while on the site, so they don't convert very well, hence a lot of advertisers don't bother and their inventory sucks. I've never seen an ad on Facebook that highly targeted me. I think that beyond a few niches (like engagement rings) Facebook's targeting works out to be a wash. That's why despite having 300 million users and billions of page views they are only barely profitable.