I used Facebook when it first came out. I thought it was pretty useful as an enhanced version of something like friend finder. I moved away very quickly when I first graduated high school and lost touch with a lot of people I had known. When Facebook opened up to non-university users, many of them showed up and I was able to reconnect. But to me, that was its purpose, re-finding a pre-existing social network of people I'd known from school. Once I had their real current contact info and had met back up with them, Facebook didn't serve much of a further purpose. The people I actually care about I'll see in person every few years when I go back to where I grew up to visit. I don't need to know what they or anyone else is doing or thinking on a daily basis in-between those visits.

For all the people thinking "hey, you're on Hacker News" is some kind of gotcha, I think it's useful to distinguish between what all these things are. I'm on Netflix, too, which is a centrally-hosted platform that distributes algorithmically-curated media. That isn't nearly the same thing as a social network. Hacker News is a link aggregator that you can comment on, effectively serving the purpose of a newspaper, but crowdsourcing both writing and editing. You can't follow other users. You can't tag other users or receive notifications (and I don't want notifications). I don't have a profile and don't think anyone else does. We don't send each other direct messages. There is no personalization. I don't see any meaningful way in which this is similar to Facebook or Twitter. It's more like an industry conference, but ongoing, virtual, and anonymous.