Back in the day we might have a forum or a number of forums on a topic. Let's say it's Nascar Forums or whatever. I might not like the opinions of the moderators and that'd be that, I'd leave the site. I'd recognize that it's not reflective of the wider world.
Somehow Twitter and Reddit and various other social networks don't feel like that. I feel quite often that some subset people around me take opinions from Twitter etc. as being reflective of mainstream thought. When really it's still just a tiny microcosm of humanity.
I don't really use them any more, but I still have the sense that all sorts of social movements and bizarre (from my perspective) opinions and value frameworks are being born and spread there.
More and more often I find myself in conversations with people and suddenly I feel like I'm reading a reddit or twitter thread, and I'll see the conversation follow an exact path that I've seen before, only now in real life.
It's a really strange feeling as someone who has been reading people's opinions on the internet for what feels like forever, and just recently seeing those opinions show up in everyday conversations with people I've known all this time.
Edit: It's especially jarring when you see these people say things like "in my opinion" or "i think", because now I start to wonder "do you really? Or did you just see somebody else say that?" Not that all my thoughts are original, but I don't take credit for things like that.