The ability for ads to target individuals while being invisible to others is something quite new and pernicious. If you advertise on television, your commercial is seen by everyone watching. If you run an ad in print media, everyone who has a copy can read it. Individually targeted advertising is ripe for abuse. If you're interested in reading more how this is really qualitatively different, I highly recommend reading some of the work by Zeynep Tufekci https://en.wikipedia.org/wiki/Zeynep_Tufekci