Though...what happened last time was that a lot of insightful long-term contributors were accepted and then disappeared off the face of the site while they worked on their startup. Meanwhile the folks leftover were all the ones trying to make themselves look good to YC at the last minute.
Eventually it rebalanced out. The short-term folks got bored and left, while a new crop of top posters grew out of the ones who weren't ready for YC as of the summer but were going to become startup junkies anyway.
I've noticed the same thing. There's really just a handful of News.YCers I recognize that have posted consistently since before the last round. Incidentally, its these folks who's opinions I value the most (for the most part).
Oddly enough, I find that I don't pay too much attention to who writes what. The size and color of the usernames, combined with the fact that they're rarely capitalized, means that I usually take note of names only as an afterthought.
You bring up an interesting point. On one hand, to be a part of a community, one has a responsibility to contribute from time to time. On the other hand, if you practice what you preach, there probably shouldn't that much time available for posting...
Eventually it rebalanced out. The short-term folks got bored and left, while a new crop of top posters grew out of the ones who weren't ready for YC as of the summer but were going to become startup junkies anyway.