It depends heavily on how 'what is being advertised' can be related to 'what people are interested in'. For example, I ran a small business creating posters fr

It depends heavily on how 'what is being advertised' can be related to 'what people are interested in'. For example, I ran a small business creating posters from cyclists GPS data. I created FB ads that targeted people that used Strava (I'm a little rusty on the exact terminology but it was "had an interest in the strava.com website") and got lots of clicks with people that tried the service. However there are topics - window blinds is a good example - that people aren't (in general) interested in for very long - so once the algorithm comes to the conclusion that you like blinds you've probably already made a purchase. Similarly I subscribe to the economist magazine and keep seeing Economist ads - infuriating. Facebook allows advertisers to remove groups of users (for example those that have purchased a product already) - I don't know why more companies don't use this. You mention charities - I remember reading that most charitable donations come from people that have already donated to that charity before, although I can't find proof.