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That's addiction disguised in adoption

Yes, only if it's a stretched marathon, otherwise it may relapse.

Twitter and FB are still doing the adoption campaign. It is a never-ending process.

Adoption here is in the context of reaching critical after which engagement will switch to autopilot mode. At that time, adoption does not remain your primary business anymore.

I know but it cannot be neglected at any point in the product's lifecycle. The approach changes yes but not the adoption.

Adoption here is in the context of reaching critical mass, after which your adoption campaign does not remain the primary business anymore.