Good problems should be promoted.
Not all people rate (coolnes) of finded good or bad problems.
So how can we find which problems are good and interesting?
People add to their favourites only really good (in their opinion) problems, so I think that a way to sort problems by count of how many people add problem to favourites could be really usefull thing to promote good problems, and a simple way to find brillant (dicovered by others) problems.