Currently none --- but only because I don't use Facebook.<p>Hear me out on this. I'm not convinced it is necessary for users to pay in most cases. The only reason to pay for a service is if there is no <i>free</i>, privacy respecting alternative.<p>For example, DuckDuckGo is a reasonable search alternative to Google and Bing with no payment required and no privacy invasion. DDG is driven by contextual advertising. Lots of other services <i>could</i> be built around the same model.<p>In my mind, Facebook is the #1 example of a service that would be difficult to sustain for <i>free</i> without privacy invasion only because it's very nature is so personal.