> They make lots of money because their ads are effective, because they target them using data It is easy to see that they are using data to target users, but

> They make lots of money because their ads are effective, because they target them using data It is easy to see that they are using data to target users, but do we have data that shows how effective are they ? The fact that everyone is using them doesn't necessarily means effectiveness, it could simply be due to popularity (big user base), ease of use (you buy an ad once and get a lot of coverage, good or bad) or managers being afraid to go against the stream.