Did you once have a myspace page or live journal where you said very controversial things or vented angst in a manner that you'd rather your co-workers didn't see? Well sorry but all that stuff now goes into your facebook feed where it will be with you forever.

It takes real determination to stay actually anonymous on the internet today and someone trying to stumble into it is likely going to screw it up - when we millennials were growing up that personal data you accidentally leaked onto a forum (maybe during a spicy exchange of direct messages) can't follow you since that forum no longer exists - it was probably hosted on PHPBB and either an admin accidentally deleted the DB at some point or the whole server was chucked in the trash - even if someone had access to those messages it would be harder to definitively tie it back to someone since user fingerprinting was so non-existent.

That all said, I was in the middle of University when folks were learning that bong-shots on your facebook page might hurt your long term job prospects so we did get to see it start to emerge as a concern.