If targeted advertising does not work, then the only remaining business for Facebook is spying on people:

Targeting to super-specific audiences was expensive but didn’t result in a big difference to its business, P&G CMO Marc Pritchard told The Wall Street Journal. The company, whose massive portfolio of household brands includes Tide and Crest, had experimented with Facebook’s most sophisticated targeting tools, which allow advertisers to reach a narrowly defined audience.

Source: Why P&G Decided Facebook Ad Targeting Wasn’t Worth the Money | Digital – AdAge