Do you mean like Ashley Madison hack?<p>Nothing in the ad-backed company model prevent someone sending a fake advertisement to the demographic who are likely involved in adultery. After that you publish a &quot;people who subscribe to this service are ...&quot; list based on who clicked on it.<p>The only question if someone could do this with Facebook&#x2F;Google is if they provides targeted advertisement to that demographic or if you have to provide your own algorithm and combine different targeted advertisements with the available demographics.