[Stats]Extrapolating the current "average posts per day" stat rounded to a nice 8000, we get 248K posts per 31-day month. Now, consider the post totals in mid-2013 and onwards. Signature campaigns were not nearly as big back then as they are now, especially in regards to bounties which make up the bulk of the spam.
Bad traffic will drop. Good traffic will increase.
Although, this is an interesting statistic to look at, and vaguely base it off. However, when considering the amount of exposure Bitcoin has since then, and the popularity that its gained through price surges, and whatever else. I wouldn't consider that a fair test. No doubt bounties bring a huge amount of traffic to the forum, however that's also part of the cryptocurrency world now, and I'm not sure if I'm willing to class that as bad traffic. After all, not everything in that area of cryptocurrency is dodgy. There's a lot of shit to wade through, but its got some promising ideas among all of that.
We only have to look at the top sections for total amount of posts on the popularity of those. However, considering bounties require users to make multiple posts that figure is also a little skewed. Some threads in the altcoin section you can literally go through a whole topic, and end up reporting 99% of the thread which is like 60+ pages long. This has generally reduced recently, and older threads are more subject to this.
Also, when comparing the amount of posts from the altcoin section to the Bitcoin section we have to consider there are a lot more alternative coins out there which appeal to a larger audience than just Bitcoin. This would then attract a larger audience generally. Although, Bitcoin is considered THE cryptocurrency by many, a lot of users will be looking to invest in new, and upcoming alternate coins because they offer something different. This is why we've seen such success with coins offering lower transactions fees, and faster confirmation times.
My original point is that signature campaigns aren't the sole reason of the vast activity difference between the Bitcoin sections, and the alternative coin sections. Although, of course its going to have some sort of impact on those figures its just hard to gauge how much of an impact that has had.