This is more about about promoting sharing as a cultural behavior than making money on this particular product. By incentivizing sharing, companies end up with

This is more about about promoting sharing as a cultural behavior than making money on this particular product. By incentivizing sharing, companies end up with more personal information. It forces lurkers to participate (some might argue that's a good thing). The service forces you to pay for content with your own content, whereas before the payment was implicit, or at least invisible -- as long as you were in the store, you consented to being monitored.