I realize that we have these issues, but anything that's not going to make it take way too long for people to be able to submit isn't going to help the signal/noise ratio much.
It's kind of presumptuous and pompous to assume that just because someone hasn't been on HN, they don't know hacker culture through some other means. HN may be "hacker news," but plenty of hackers aren't on HN (even though it may seem as if everyone is on HN now).
And the more emphasis we put on karma, the more people will do things with the intent of enhancing their karma rather than enhancing the discussion.
On the other hand, you could have long-time lurkers with no karma that are unable to submit and that could be a problem. You couldn't base it on length of time registered instead of karma either because then spammers would register accounts and sit on them before submitting garbage.
I think think that's a problem. If someone is just a lurker they aren't really fully a member of the community the way a poster is. And when has posted plenty of comments, gotten up-arrows for some and down-arrows for others, they have a better idea of what community standards are.
On the other hand, neither do I expect to submit anything very soon, so I suppose that not being able to wouldn't matter much to me (until I want to submit something, of course). It would be quite interesting to see statistics for who submits articles, and how many comments / points they have, and how long they have been a member.
It rules out people who have not interacted with the community at all, without turning HN into some exclusive "members only" club.
What happens if this guy heard from someone that people here give good feedback abt his new idea or startup? Should he wait for long (like 2-3 weeks to get 25 or 50 points) to get feedback? So I'm a bit biased about having posting thresholds for new threads.