It's pretty unfair to say Mayer ruined anything. She didn't save Yahoo, but there is no evidence it was ever in a position to be saved by her.
Mayer's performance had nothing to do with her gender. I'm adding this statement to respond to some other peoples' comments.
I also wholly agree that diversity for diversity's sake is idiotic. Can't wait to read The Verge and Ars Technica spins on this one..