Interesting stats for signature campaigns and I hope you will manage to update this on regular basis ^{(easier said than done)}, but I don't think Stake members are all writing maximum number of posts.
I don't think that number of participants is always increasing visibility of specific signature campaigns, it all depends where and how members write their posts.
@rby maybe you can include CoinSlotty campaign in you list, we started with small but mighty group of people, and soon this should be expanded to more members.