That's not even enough anymore. You also have to make sure that every one of your contacts do not upload their address book to conveniently find friends like you who may or may not be on the network. And that they don't tag you in images, events, etc.
You're an entry in the Facebook database, whether you have or have had an active profile or not.
...but that's such a myopic view of the problem. Facebook has this data. There's an entire market, intentionally kept from the public, that specifically deals in the selling and trading of profile data. This is why the concept of "shadow profiles" is important.
Let's say I have three friends who are on Facebook and I am not (which I'm not). Those three friends upload my contact details to Facebook and, from these three data points, Facebook can derive certain assumptions:
Sex from my name.
General age-range based on my friends.
General occupation (let's say all three are co-workers or previous co-workers)
General interests based on their interests. etc.
So, now Facebook has an ad-targeting profile of me. All they need to do to get more information on me, regardless of I'm blocking their specific domains, is to purchase correlating ad-profiles on what I'll call the advertising market.
So, my credit card purchases, my Google search history, etc. can all be correlated back down into this one shadow profile that Facebook holds on me and this can, in turn, be used to target ads to my friends. Not only that, but if I ever do sign-up for Facebook, they can immediately start targeting ads to me. (read: I'm not a net-advertising loss for being a "new user".)
I'm not saying that you shouldn't block Facebook domains but I think that, in the overall scheme of things, it's tossing a drop of water onto a raging bush fire.
It is currently impossible to remain anonymous, regardless of whether you participate in the system or not.
In my case, given the density of my network on social media, and their propensity to fall for dark patterns that siphon private information - had I never owned a computer and lived off the grid, all the major tech companies would still know my: name, age, address, contact info, hometown, family members, income bracket, ethnicity, general dna (many family members did dna tests), and more.
Shouldn't I have a say in any of that? Shouldn't things like address book importing be restricted/illegal?
Why would any politician fight this? It's a platform they all use to gain/sustain popularity, and it's the official national communication channel for the US.
I don't _think_ Twitter or Facebook are doing backroom deals with every prepaid sim vendor to be able to tie that phone number back the the identity used to register the sim card.
I wouldn't suggest you use this to register your Dream Market vendor account, but I doubt you'll end up with targeted advertising based on your other real-world web/app behaviour based just on the ID provided for a single-use burner SIM...
You don't need to show any ID in Europe to buy non-contract phone number. You can go into most stores and get free or pay 1-5 euro for a phone number.
Even before that prepaid phones have been a strawman argument, actually maintaining a 2nd number in the long run is quite a bit of work since it usually expires if you don't use it enough.
For some platforms, even this is not an option. Case in point: LinkedIn (owned by Microsoft). I get "friend" suggestions about a friend that I know is not on LinkedIn. He's absolutely social-media averse, and would never be on LinkedIn (or FB, for that matter). But LinkedIn continues to claim that I can connect with him.
How did they get his email address? Because some third person (who emailed both of us) probably shared his contacts with LinkedIn.
Unless you are an EU-citizen.