I +1 for the overall insight, but it's logicial and desirable to have small communities of people alike. As long as you have many of them, that are all very different and their members are part of several of them. It know it's the case for me (I'm part active on HN, reddit, imgur, twitter but IRL in sport, charity and porn), and I believe a lot of people are too here.

So I think we are OK.

HN is indeed a bubble, but it's a fantastic one that would lose a lot of value if the liquid it came from was diluted.