I was a regular reddit reader(in fact at the time I was a digg-refugee) and found HN about 6 months ago while reading about YC. Reddit started to disappoint me more and more(e.g. Ron Paul) and I started to frequent HN more often. I am kind of disappointed about reddit and digg, that they weren't able to maintain the quality of their active members. I am not quite sure if PG succeeds in protecting the value of HN without making it to a closed community with an elite group of moderators. Let's hope he'll find a way to do this.

I think the most promising method would be in limiting the weight of new users. Not giving them any weight in the voting would prohibit them from posting stories that don't fit into the topic. If they stick around long enough eventually people will find out what the community likes and will submit similar stories.