Earlier quoted context omitted.
No, the massive income Facebook generates only imply that the people spending money on targeted ads believe (!) these ad are working. It is not a prove per se these ads really are worth their costs.
Buyers have access to a detailed audit trail of their ads and campaign activities. They see where ads they bought ran, the number of people who were able to see their ads, and clicks and other interactions with their ads. If "these ads are working" is defined as "these ads are accomplishing what they were intended to when purchased," peoples' spend is founded more in data than belief. Buyers have access to ~2BN peopl…
The fact that people buy ads is not at all evidence that they are effective.