Well, I certainly do believe in them...
...but I don't believe that they have supernatural powers. They can't make the price of gold go up and down on a whim (without leaving big fat obvious fingerprints). They can't control the government or the weather or my mind. They are just people.
As long as they keep their activities within the law, then they are entitled to their secrecy. If their activities stray to the wrong side of the law then they likely will be caught for it, sooner or later.