Isn't the entire idea of the cloud a massive correlated risk? If AWS is hacked, it would be very bad. That said, experience has seemed to show that people who build infrastructure tend to make less mistakes in that way than the millions of people who are building businesses and personal sites would. I agree that in a perfect world security would be easy to get right and federated, but it seems like it you have to pick one 'right' is the best choice for now.

Do you use any cloud providers?