The first question would be: "Why do we have the board in the first place?"
Historically, I think it was to replace the Top Contributors, All Time leaderboard, which had become stale since at least half the people on it didn't post frequently anymore (and at least one of them had left permanently). I think that one had existed both for motivational and reputational effects. (If you want people to respect and listen to the top 10 posters, it helps if they know who those are.)
I'm wondering what the optimal number of people on the leaderboard would be. I suspect that people who appear on the leaderboard post more often because they want to remain on it. The other advantage, is that if the leaderboard seems in reach, more people will compete to get on it.On the other hand, if too many people were added to the leaderboard, then "being on the leaderboard" would be worthless and people would only care if they had a high position.
There are currently 15 people on the leaderboard. I suspect that if there were 20 people on the leaderboard, that would increase the motivation effect, without significantly devaluing being on the leaderboard itself.
What do people think?