Well, what has been discussed here seems to be the people that do start 5-10 threads in a day.
Often not with a real message, but with a sentence intended to spark provocation rather than good debate,
and they are often hit- and run.
There is also the problems with bots registering (here or elsewhere) and flooding the forums.
A limit in threads pr day/ week would reduce such things. I.e. all these black magic threads that appear every now and then.