The Number 1 stupid thing is simply being a whore.

There are exceptions to every rule, like Cameron or Gia and a few others, but the vast majority of whores are stupid women with absolutely no other marketable skills or any other prospects. Which is why you end up with all the other stupid things they do. Sure, you have ones who are smart in a manipulative sort of way, like Lubben, but for the most part their highest skill is to lay down and have their holes filled at the direction of men.