Happy families are all alike; every unhappy family is unhappy in its own way. With banks, it should be the other way round.

For too long banks were too alike and this created a very unhappy state of affairs indeed: ranks of identikit firms all trying to be all things to all people. Now future happiness appears to lie in differentiation - pick what you're best at and stick to it. That's the theory anyway. The trouble is, it's going to make things very complicated for banks and their investors alike.