If only! Facebook collects plenty of data about non-members.

I have a hard time considering it "voluteering" considering other people can put data about me up on Facebook and I have no recourse.

Further, I fail to see why "voluntering" it is relevant at all.

They allow users on from the age of 13. It is rather unclear to some children that they are consenting to mass surveillance, rather than just trying to fit in with their friends

I don't have a strong position on the broader issue, but I feel like this argument ignores some context. It's one thing to sign up for your local car wash's loyal program and have them do some lightweight customer research on the data. It's quite another for to input your demographic info and interests into a social networking site and have it be analyzed by some of the most sophisticated data analytics in history. The potential downside/cost to the user is orders of magnitude larger. I think it's a stretch to say the user is giving informed consent to (for example) have their manual photo tagging be used to train a model so that a computer can identify their friend's faces automatically. The average user has no idea such a thing is even possible.

You can't claim "Caveat Emptor" when you have no means to know what is happening with your information.

Actually that's a reason why we need laws like GDPR: I don't have an Facebook account but random websites I visit still have elements embedded from Facebook. I've never agreed for Facebook to store my data but they can only give their word they won't collect my data (which, AFAIK, they don't give).

I've got no recourse against this - or maybe I have because Facebook is big enough that it's worth it to create targeted block lists. But against the next 20 smaller companies who do the same?

This is why there needs to be something else than just blindly trusting everyone out there. Because someone will not play fair if theres a competitive edge to gain.

My usage isn't voluntary. I am pressured. There are friends I can't reach other ways.

Mfw you act surprised because your airline is selling pictures of your dirty laundry because you clearly consented by giving them your luggage.