Actually, I think that the brevity of so many celebrity relationships is because they are like the rest of us, in some very important ways. It’s easy for an ordinary guy to look at some hot starlet and thing “Man, I’d love to be married to her”. But we’re not basing that on personality, or interests, or any of the things that are really important in a marriage, but just on superficial things like looks. And so it’s just as well that we don’t have a chance with them, because if, say, I were to marry Scarlett Johansson, or Keira Knightly, it almost certainly wouldn’t work out. Well, a hot male celebrity will think that those ladies are just as attractive as any of the rest of us would, and will have the same “I’d love to be married to her” reaction that a normal guy would have, except that in his case, he does have a chance. And so celebrities go ahead and form relationships with celebrities, just like most of us think we want to, and the relationships fail, just like they would with most of us.