I don't doubt they work. I doubt the margin of work done by facebook ads on working professional adults over the work of ads that they are exposed to through other means and by word of mouth. And not that that margin doesn't exist and not that it's not worthwhile to advertise on facebook, but the doubt is that as compared to any other demographic being advertised to that it's worth so much more.

Advertising to impulsive spenders is worth more than advertising to less impulsive spenders. Less impulsive spenders are informed by ads, more impulsive spenders are convinced by ads.