Web3 applications will require users to have tokens so they can interact with the DApp, so either a network token like Ether or a utility token like BAT is needed. The tradeoff is that your data isn't mined and sold for advertisers and your content can't be demonetised or otherwise censored by the platform. In the context of social media, I believe the cost will serve as deterrent to trolling and harassment.

For all the hurrah about Facebook and privacy, it will be interesting to see if users really do care enough about their rights to free speech and privacy to switch platforms and put some of their own resources into making better solutions.

https://www.youtube.com/watch?v=ERuSGa4UPow