Logically no one. People go to LinkedIn and other work-related sites. BUT facebook being who they are and tracking you in (almost) each and every website on the planet (that silly like/share button) they "know" that you are job hunting and leverage on that knowledge.
Ok, more to the point, do they really expect prospective, quality engineers to click on facebook ads? Especially for someone with the brand recognition (for better or worse) of uber.
My guess: You're targeting people who waste their precious time on Facebook. And if they don't value their own time, they probably won't value yours either.
