I think the other problem is the maximum that the campaign pays out. If they just copied every other campaign that required only 20, 25 or 30 per week (I see the average is about 25 per week) then we wouldn't have all this spam and low quality junk.
The massiveness of the campaign also indicates its potential longevity. Too many posts. Too many users. Too much payments to too many people = short lived campaign. Controlled ones tend to last months or years.
I'll be grading a campaign and see that some users do their 25 posts over the course of 1-2 days. Then they do not login again til the next week. I normally issue a warning to a user when I see this and if they do it again, remove them.
Another issue when speaking about junk posts is your view on junk/spam may be different than the poster or mine. This goes for the whole forum. Everyone's view on what is or isn't spammy is different. Everyone has a different idea of what should and shouldn't be allowed on bitcointalk. I think part of that problem is certain sections shouldn't be allowed to be counted in any campaign. Mainly all the discussion boards sections. Those sections are filled with tons of junk threads that will only bring junk responses. Unfortunately, the users junk responses are on point and about as constructive as can be given the thread and its content. Ultimately it is the managers decision on what's accepted or not accepted, but it's not as easy as well you post junk you're out.
With cryptotalk I have no control over the sections counted or not counted, so I cannot implement this sort of rule. I would suggest that most users in the campaign only look to make 5 or so posts per day. Worrying about making the max everyday and getting paid will only hurt you in the long run. Not only do you have to worry about me banning you in the campaign, you have to worry about losing the account. Just because the rules say you CAN do 20 per day, doesn't mean you should.