Yeah, that's why I only somewhat included it. It's tougher to follow specific people. But it is possible if you keep a list yourself of interesting accounts and check in later on what they've posted.
But the dynamic is definitely different and seems a lot more anonymous unless you are a really high profile account like antirez, patio11, drewdevault, or a CEO of some well known company or startup.
Perhaps it would be easier to enumerate the things that aren't social networks. Does the postal system constitute a social network, at least in the literal sense of those words? Maybe! It's a network that facilitates social interactions after all.
Why wouldn't we? Pseudonyms? Reddit is considered social, I think, and that tends to be even more difficult to map to IRL identity.
Edit: just barely not inb4!