That's true, but there's also an advantage to that. It's possible to learn a lot simply by osmosis of reading this site. This does lead to some bizarre groupthink though.
I've also seen many people who learn things incorrectly and do harm to themselves from reading this site and others as well. It goes both ways and totally up to interpretation. As I once crossed a book in a bookstore which a cover which read "It's not what you say, its what they hear". Everyone interpret everything differently and sometimes this could be good and sometimes it could be bad. I think its all in perception.
I still have somehow trouble with these high numbers. By looking at the front page, the points for top stories are still staying relatively at the same level. These relatively low numbers of votes makes it still seem to be a relatively close community but maybe just many of the new visitors can't be bothered to participate.
I assure you these numbers are real. I have no inside knowledge, but I have submitted a few StackOverflow posts (with my username attached to them) that made it to the front page, and I watched how many of them were from my link on HN.
(there was another one with about 200 votes, but I didn't find it!)
Compare these to submissions like this one, that has 350+ upvotes already, and I think it's realistic to assume at least 60 or 70 thousand unique users (I mean users in the sense that they know HN and visit it consciously) visit HN every day.
"why so few people vote or take part in the discussions."
To vote or participate you have to be logged in.
Would be interesting if PG released some data on logged in visitors.
Also, isn't the amount of votes the amount of net votes? So you could have 100 upvotes and 60 downvotes to net 40? (Of course that still doesn't jive with his numbers which I agree were very interesting and unexpected I would have never guessed that.)
Not participating could be also a) a confidence issue or b) lack of ability to type or use of a particular keyboard (I never comment from mobile for example).
Still, it doesn't explain the discrepancy in the numbers.
I don't know about the reason behind low number of votes, but the relatively low number of comments could be because the general attitude on HN (for the most part) is to be silent unless you have something constructive to say :)
For example, I don't know anything about python for example, so anything I can possibly say would be completely un-constructive (except if it's a question), so I shut my mouth and don't say anything; even when I see a (provocative) comment saying Node.js, which I really like, is shit and we should all be using python.
I've done my share of posting useless things on this site, but in the paste few months I've tried to not waste other people's times with useless comments and have removed maybe 40 comments (I would write a comment, read it and see it's not important and don't press "reply").
"to be silent unless you have something constructive to say"
Interesting. I tend to read much more stuff that I find interesting and have something to say rather than stuff I know nothing about.
"removed maybe 40 comments "
I don't think I've ever done that. If I get moved enough to comment I feel what I've said is important enough and the only thing I don't like is a downvote w/o explanation which is inevitable.. Actually it's the thing that I find fun and addictive about HN. I can usually predict downvotes as well on things that I say.
Would be nice if there was a way to post (w/o logging out) anonymously from time to time. Say once someone gets to a certain karma level they have the ability to say what they really think w/o fear of downvotes which I believe does supress what people think.
My hypothesis is that the majority visit HN to learn from those that do participate. Of course, their learning would be most effective if they participated themselves.
It's the nature of web forums. I run a subreddit, we get 100 uniques a day, roughly. Generally they make about one submission per day, collectively.
I'm told that's a pretty normal rate on reddit, given our size. It's easier to consume than to produce. (nb. People may be producing more elsewhere while not participating here)
I find the same effect on HN to be even worse. HN now has over 100k uniques/day[1] .
That means that on any topic you'd ever like to comment on, odds are good there are many HN visitors who are better at that you are.
[1] traffic from last year: http://ycombinator.com/images/hntraffic-9feb11.png)