This had existed, for Twitter at least. Apparently it shut down last year. I had ended up on several blocklists or at least one commonly shared once because I'm blocked by a good 20-30% of Twitter's blue checkmarked journalists that I've never once interacted with or Tweeted at before.
I could easily see being randomly blacklisted/blocked with no real understanding as to why you are blocked other than some well-connected person that you peeved off once had added to a shared blacklist. This likely already happens.
Anyway, I remember pointing out at the time that the Data Protection Act had been used to shut down corporate blacklisting efforts run by people with very good lawyers and much cleverer attempted loopholes than theirs, and that their chances of somehow finding a loophole where everyone else had failed were basically zero.
Does that mean Uber and Lyft sharing lists of drivers that have been banned from their platforms is illegal?
Corporate blacklisting is illegal, but there have been substantial carve-outs in the name of safety. DISA [1] is a great example of this - fail a drug test and you're banned from about 10% of the US economy for 7 years.
I really wish people would wake up to the fact that right now, computing is still in its "enumerative innovation" phase where the computer will get thrown at every human problem under the sun to see what sticks, or what causes complete outrage and cannot be allowed.