@OP, I once read a comment where jokers once said some numbers of karma is actually required to achieve a certain rank on the forum but I don't think that the rank requires karma is the legendary rank. If you look around, you will discover that their are different ranks, badges and positions after the legendary rank, which I believe that it's some of those ranks that actually requires the number of karma an individual have.
Also, do you know what I think? It has been known that karma is given to individuals that make quality post, so I believe than in the future, campaign managers may also start to use the karma as a criteria of selecting usser into their campaign because they may believe that only the users that are earning karma are the most quality posters.