The last time I felt that - where I felt like I actually knew people, where I could sometimes tell who wrote something just by the writing style - was Groklaw. That's been a while. Currently, of all the places I know, HN comes the closest, but I don't actually know any of you.
Of the new internet, Facebook comes the closest. You could use Facebook in that way, and some people do. I think my wife does. But she's not in her 20s...
I wonder if the 25-and-below crowd still needs personal connection, but doesn't understand how to go about getting it. So they use Facebook in a way that is different from how older people use it. (Or maybe they just don't use Facebook - that's for old people.)