Joke threads are still when all is said and done a tiny percentage of forum space,no more so than all of the whats your favorite threads etc (of which I have started a few) the same rules apply as to any other thread if you don't want or are not interested in the content then don't open and read it.
I am all for jokes but perhaps as CC suggests maybe one joke per thread, although this could lead to people opening new threads just to get their jokes in.
We perhaps should let things run as they are at the moment if it was to become a problem then it might have to be dealt with, the chances are most of us will get fed up posting jokes and take a break for a while anyway.

Just my tuppence worth

NCM