Forcing users to 'prune' their status updates is in fact a symptom of something broken in the user experience. I check into Facebook every now and again, and I shouldn't to have to act like a gardener who has ignored his back yard for a month. A lot of status updates are incredibly frivolous too - Facebook's culture is not suited to my taste I guess. Virtually all of my (Facebook) friends are not hacker types and will post "I'm bored" or "feeling tired" or something equally awe-inspiring. Granted, this is something that Facebook would have never solved as they are trying to appeal to the mainstream, not early adopters. I love the fact that by logging onto HN I often learn something new, and quickly learn to a) write well and b) only talk about stuff you are knowledgeable about. Anything else and you will get caught out pretty quickly.

(2) The whole thing about the Dunbar number

This had occurred to me also when writing the original comment, but I didn't mention it as I don't see a decline as inevitable as an online community grows in size - I believe HN is proof of that. By deliberately appealing only to a narrow segment of the internet population through a strict, human-enforced culture (see HN guidelines), and allowing users to only maintain very loose ties if any with each other (contact info in your HN profile for example), it's possible to have meaningful, no-spam interaction on an online community. Pg mentioned recently that HN now gets something like 60k uniques per day. I've been on HN for quite a while and I think the quality of article and comments has been consistent over time. I think the Paul Buchheit philosophy of building something that a small number of people love, and that most people would hate (HN), rather than something that tries to appeal to everyone (Facebook) comes into play here. See my below comment on the 'tribes' concept for a possible solution to this problem in a social networking context. I believe it would work as it models how people organise themselves into groups in real life.