It’s not only FB data that they are harvesting.
Yesterday whilst on FB, I had my mother’s handyman pop up as a suggested friend.
The only way that FB could have made a connection is by searching my Google contacts.
The worry is what else is FB looking at?
As I said earlier, if they can, they will harvest data from you’re phone book, call records and more as well. I only know about Android, but this sort of harvesting can only be done with explicit permission, but then most people just click ‘yes’ if it asks a question without thinking, or even reading the question in a lot of cases.
If you want FB to not do this, then you need to be careful what you click. You can also disable these permissions after the fact, but by then it’s almost certainly too late. Some apps, I know will constantly nag you to enable certain permissions and I’m sure FB will do this. If you look at the T&Cs for the free tier, you may even find that this is mandatory.
Edit: I don’t think an app can override asking the user for permission for certain things, but if it’s possible, I’m sure FB would have figured out how to do it. I think you can add several permissions together into a single request, which may be how it’s done.
They’re far more clever than that, using things like proximity, frequenting the same places, friends of friends, in the same Facebook groups and much much more.
Although I dont do it myself, watermarking your photos with a copyright mark would protect your photos as the the big companies claim them
Claim that they have copyright??
I think that you will find that you grant a perpetual, worldwide license to FB for everything you put there.
Wouldnt be at all surprised, I really dont get involed with any of these shite companies.
Purely out of interest then, how do you communicate with friends and family world wide if not FB, Skype, email, sms etc.etc.?
I use FB only for the message thing, I would prefer email or even text but most people I want to talk to prefer FB, Instagram or WhatsApp.
Just wondering @Corona for my own interest of something I may have missed. 
Edit: I don’t have, and will not have, a smart phone. 
Whatsapp or signal.
Whatsapp requires you to have a smartphone. Does Signal? I was looking at Viber the other day and, while it will work on a desktop, it, like Whatsapp, requires initial installation on a smartphone, as I understand it.
Facebook!
Then there is the old idea of actually calling friends. 
I’ve just had a brilliant idea that no one can hack or steal the info. I found a pen and some paper and eventually remembered how to write (not very legibly TBH🙄). Apparently they are called letters and can be sent by post.
I agree! Somewhere over the years I’ve forgotten how to write.
History shows us that sending letters in the post has definitely never been hacked. No one’s ever intercepted a piece of paper travelling by road, rail air or sea on its journey between two parties… 
Yup ! WhatsApp listens to your shit and sprinkles it in the direction of Google.
So much for end to end encription.
When FB bought it they promised not to share numbers / contacts etc between the platforms. That lasted all of 18 months. As soon as they bought it I got Telegram and Signal instead.
I’m sure that call content is encrypted but the metadata is also valuable i.e. who’s calling whom, who’s in which group etc.