I just counted, and in all signature campaigns, paid in bitcoin around 415 members participate. I did not count the Stake campaign because I can't find the participants list and 1xbit for obvious reasons. Plus other campaigns where payment is in tokens, I believe there are about 1000 members in total who are paid for their activity here.
maybe Loycev or someone who deals with statistics can provide information on how many regularly active accounts there are out of 3.5 million registered while "only" 1000 paid for that.
According to ninjastic space, ~9600 members wrote at least one post in the last month, and that includes all those altcoin bounty shitposters that are spamming their "proof of authentication" and other nonsense. Exclude them and what's left is maybe ~5000 members. Small number of active members I think, considering how many registered accounts are there.
in the end, several other forums tried paid to post and none of them survived.
That's because none of the had an actual community built, like it was the case with bitcointalk.
I'm afraid that if Theymos were to suddenly ban campaigns and bounties, bitcointalk would suffer a similar fate. It might not, given how popular bitcoin is compared to even the hottest altcoin, but I can almost guarantee you traffic would drop off a cliff.
Exactly for that reason there shouldn't be no fear that signature campaigns will be removed anytime soon, as everyone is well aware of the effect that would have on forum traffic.