[macando]

You are right. Ephemerality and velocity is what influence the current state of social. With forums you had a community (often local) with a common (usually offline) interest. You had permanent topics and memorable members. I frequent subreddits which grew from 10k to 200k and 100k to 1M subscribers and I haven't memorized a single username. Maybe a creative troll or two but even they eventually gave up. Maybe all this is caused by a rapid growth and a lot of new people still figuring the things out.