Built on exploitation? In my opinion built on utility supplied to customers.
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Facebook's utility for me is now near zero, possibly negative. I'm only there because mom is there. Mom's only there because her friends are there.
Moving out of that morass - at least, until mom stops using computers is impossible.
At least with Amazon, Google, Netflix, Apple, Microsoft, etc, I (currently) have meaningful alternatives.
Network effects suck.
Why should that keep you there, though? She's your mother. Surely, you can talk with her directly even if she is on Facebook.
How this is legal is astonishing.