Even if it has a social aspect to it I wouldn't strictly call it a social media. It looks more like a fucked up mix between a web forum and a tool like stack overflow.
This. I draw a line between 1) sites where the author of some content is very visible and 2) sites where you need conscious effort to check out who wrote something (like reddit, HN, wikipedia). The former is social media. The latter is just web 2.0.
I feel like reddit is the biggest site that no one talks about using.
A site with accounts that you never want linked to your real self, or your other accounts, under any circumstances. It bucks the trend of every profile linking to every other one somewhat