Rather than banning, they should simply be moderated/regulated. It should be 1 post/day max since that's = 1 activity. Then, if sig camp posts get merit, there should be bonus. It seems useless to post more than once a day but there are days when someone probably is "in the mood" and has a lot of great ideas, just like writers, so.
If you observe the services section a lot of changes are already taking place:
1) There are additional payments for members with merits. I think this is really a nice initiative taken by campaign managers and will ensure that only quality members are being chosen.
2) We cannot enforce strict requirements like only members with merits can participate simple because this system is quite new. Many members are getting used to it and thus it is not right to deprive them of opportunities completely.
3) I do not agree to making limits like 1 post a day. some members might be able to give tie here only on weekends because of their jobs or other works.