Joke? No, it isn't. There were some non-mainstream social media platforms that I see who have their own crypto. One that I remember is Clouch.com. For the mainstream one, we have Facebook. Yes, you heard it right. Facebook also planned it before but I'm not sure if the plan was postponed or what, since I never heard an update about it. Their use case is obvious already and that is, they will be used as a currency inside the app.

Mainstream social media sites are mostly centralized but again, there are non-mainstream social media sites I see that are decentralized. They are related to crypto of course, so users have the ability to earn free coins by simply becoming active to it. It's twice better than on what is popularly used today.