1) It disincentivizes lurking. If the premise is "don't let me trip over you until you've learned the ropes" then simply observing for a certain amount of time will satisfy that criterion. On the other hand, fifteen Redditors descending and saying "DAE REDDIT!??!!???111" results in fifteen users with fourteen shared posts each. 2) The contribution of someone who sees much but says little will almost always outweigh the contribution of someone who says a lot. Your proposal punishes these individuals. 3) In a subreddit-like system, your proposal is indeed one way we control for spam. However, that's a moderation-based system whereas Hubski functions on a user-based system. I, personally, as the current moderator of one and past moderator of five default subreddits, hold much more faith in the healing power of time than I do in the multiplicative power of votes in conforming a user to the prevalent culture of a community.why not something like "ignore users with less than X posts" instead?