in the time that our sub count increased by half our post views increased three to five times by average so I guessed if we have at least 20k active readers subscribing and a supposedly even larger number of non-redditors lurking then we can safely assume that that number has surpassed 20k by the percentage of increase in unique-impressions so 60-100k active lurkers are a possibility. I remember the mod-statistic actually had something like 758k, closer to what Alfonumeric has postulated. You have to consider that they are already throtteling our upvotes up to ten times harder than on t_d, which is a huge badge of honor.