I usually am not one to make such comments, but a recent trend in HN has been submissions unrelated to the guidelines (see http://ycombinator.com/newsguidelines.html). Not too long ago there was an article on Obama and I defended its relevancy and was heavily downmodded (and deservedly so).

Digg and Reddit have become almost useless to me and HN is my main community to participate in. I have noticed that with its growing popularity, the articles have increasingly become weaker and so have the conversations. The length and depth of posts have been reduced to the level of both Digg and Reddit. People attempt to get in their "clever" one liners and the the site becomes watered down with its popularity. I strongly believe that if the community reaffirms the core guidelines to the newer users (I am quite new myself even though I was a lurker for some time), HN can retain its quality while it scales.