First, I'm not going to give any social media my ID.
If someone intends to expose your ID to hackers due to Twitter's poor security performance, this presents a perfect occasion for them.
I don't know why these social media companies are so fixated on asking for personal information. And I'm sure this is just the beginning of Elon's grand plan.
Perhaps it's time to abandon Twitter and move to other fediverse or decentralised platforms? I would love to see a mass migration.
It's optional and only intended towards Premium users, but concerning nonetheless. This ID-gathering is probably not even regulated in a lot of countries - I haven't found any info on such regulation existing. And a migration is in fact happening - but it's more of just people being less interested in the new 'X' form of Twitter with all of its restrictions. That part of the cake is distributed between platforms like Mastodon/*key, Threads, Bluesky and Tumblr, not to mention Facebook still being a thing too.
In Belgium, the RRN (SSN) is considered confidential data and its use is restricted to specific purposes, typically related to administrative, legal, or public interest matters. To ask for RRN, you'd need authorization and it's highly unlikely you'd get it just to validate someone's social media account.