[alexvoda]

That useless empty server is not so useless when the GDPR exists that mandates that platforms must provide users with a way to export data. You can import that data and convince others to overcome the network effect and do the same.

Theoretically, things like Diaspora, Friendica, Hubzilla do exist, but transforming and marshalling the potentially incompatible data is an extra hurdle. In order to migrate, users have to both overcome the network effect and abandon (retain in archive) the history of their activities.