Only if they are permitted to maintain a pseudo-monopolistic position in their market. So their own self destructive behavior, coupled with legal and societal push for options in the social network market.

The legal aspect may include legislation to forbid governmental organs and/or employees (of note) to use platforms such as FB and Twitter to disseminate and or engage the "public". If they engage the "public" then the platform must be open to "public" without restriction.