The "Cloud" is a bank of machines

There is much discussion lately of the advantages of "cloud" computing, meaning that your files are saved where your phone, tablet, computer, etc. can access the latest versions automatically, even if, for example, the file was last changed by your computer but accessed by your phone.  In conversations, I find that people have difficulty in conceiving where the files are physically located, or that they have a physical form. Logically they have to be on stored on discs of a computer being used as a server. This morning, the Washington Post published a photo of Steve Jobs in front of a blowup of the actual storage units for the iCloud. I offer this picture as a reminder that whatever one of us puts in a "cloud" is located on a machine owned, in this case, by Jobs' company, Apple. This raises some questions: Who can access these files? What kind of backup is available in case of mechanical failure or natural disaster? What if Apple changes its mind or is acquired by some other entity in the future. Is this a good idea?