This. This. This. This. This.
I believe the value of the social networking platform to a user is inverse to the maturity of the company.
Facebook has already become choked with it's own content and advertisements so the next generation migrate to a "cleaner" platform. The centre of gravity shifts. New platform monetises and the choking cycle begins anew...
The stages -
Stage 1:
Platform Exclusivity
Platform Coveted
Platform Expanded
Stage 2:
Platform Opened
Platform Developed (upon)
Platform Expanded
Stage 3
Platform Monetised
PLatform Curated
Platform Locked (to previous developers to protect revenue streams)
Stage 4
Platfrom Alternatives
Platform Decline
Platform Obsolescence
You could, quite easily Venn Diagram where the current social media services are and how they are eating the older's market share. As platforms lock developers out, other pre-revenue companies are opening up to those developers stealing previously allegiant demographics.