Sorry, but I disagree with the comment that cloud computing = mainframe timesharing, at least from a customer's perspective. Timesharing was used when you had a finite, inflexible resource which was being apportioned out using a rationing style cost mechanism. In contrast, cloud computing is an unlimited flexible resource (or is made to appear to be by the service provider using virtualisation, disk arrays, application/data partitioning etc) which is easily bought into as low cost units on a seat/app/storage basis for a specified contract period. The hardware/OS layer is completely abstracted out of the equation.