But it also gets frustrating. Conversations can go in many very interesting directions, but you can't, and you often end up railroaded down one path with the others mostly forgotten as you come across more branching points in the discussion. It feels like a Choose Your Own Adventure book where you only get to read it once.

With HN, Reddit, Usenet, or whatever, you can keep that line of discussion going at whatever speed you want.

I very rarely have rewarding real-life discussions involving more than 50 people. Online I've found tools that make this possible. Like threading.