Re: Block Facebook. Always.
No good. They'll just use it (they MUST, as they have to use say Whatsapp for work, it's a REQUIREMENT--and no, there are no other job offers) outside your purview, associate you anyway, and you're screwed through no action of your own.
You don't want Facebook to learn about you? Forget it. They can find out everything they need from everyone else: no input on your part required. Big Brother is already here, and if it isn't Facebook, it's someone else: likely some Gibsonian transnational megacorp able to get around any laws you try to throw at them.