Postdoc Rankings with several grains of salt

Though I don't place much value on these types of surveys, it still brought a big smile to my face to read that Science magazine thinks Postdoc U. is one of their top places to do a postdoc. Though that made me a little bit happier, if only for right now, I know that this varies greatly depending on your field and experiences like this can be so subjective, even in the same field or department. I'm wondering why my little bit of happy isn't totally canceled out by my clear, rational understanding of how unimportant these rankings are.