If enough people end their own interaction with it it ceases to exist, right?

If nobody gave their data to services that sell it on or use it for profit then there is no data economy.

A person would have to live a Kaczynski-like lifestyle to not interact with services that aggregate and sell data. No credit card, no cellphone, no internet. Cash only.

The point is that for each person that ends their interaction with these companies the less data they have on everyone. If only one tenth of my friends use facebook they will have less data on me than if 9 tenths do.

Convincing even one person to choose more privacy friendly choices helps a little.

'sort of' doing a great deal of work here.