The more I learn about "Cloud Computing" the more concerned I get. Tell me I am wrong. It just seems that when you centralize computing into fewer places, the more vulnerable we can get. I am, of course, talking about attacks on data centers.

It seems that if 500 companies ran their own systems, albeit more expensive, they are less vulnerable than by consolidating into a central server (backed up of course).

Perhaps I don't really understand what "Cloud Computing" is.