Are women more unfaithful than men?

In the past six months three male friends have told me their wives have cheated or have been suspected of cheating.  One friend is trying to work it out with his wife and they are going to counseling, the second friend is contemplating divorce, and the third friend has filed for divorce.  The man who filed for divorce has lost half of his assets to a woman he only married three years ago.

I was so shocked to hear these stories.  I always thought it was men who cheated, but it seems like the tide is turning and cheating is just as (maybe more) pervasive among women.

Questions:

(1) Women often stand by their man. Is it harder for a man to stay with a cheating spouse?
(2) Do women cheat just as much as men?