Recently we learned that Facebook has been using it's account holders for experiments.
You see, Data Scientists work with data.
They formulate hypothesis, then use the data to prove or disprove.
It's a science of data.
Done by Data Scientists.
Who do experiments.
Data Science experiments.
I'm not sure I understand all they ballyhoo.
Facebook offers a free service.
They have web servers, disc drivers, databases, networks, other hardware, staff, property, all of which require money to support the infrastructure.
If you are not pleased with the discovery that Facebook is using your data for Data Science experiments, you are hereby authorized to close your account and never look back.
Do what you want. It's a free planet, sort of.