Just saw this over at Amazon:

Amazon Elastic Compute Cloud (Amazon EC2) is a web service that provides resizable compute capacity in the cloud. It is designed to make web-scale computing easier for developers.

…

Amazon EC2 changes the economics of computing by allowing you to pay only for capacity that you actually use.

…Start, terminate, and monitor as many instances of your AMI as needed, using the web service APIs.

Pay for the instance-hours and bandwidth that you actually consume.

…Amazon EC2 passes on to you the financial benefits of Amazon’s scale. You pay a very low rate for the compute capacity you actually consume.

…etc.

History repeats itself… this is very close to what we used to operate with in my mainframe days. You punched out a job control deck and ran a job that used a virtualized instance of the OS. Later on you’d get billed by so many seconds of actual CPU time, I/O bandwidth, and storage. In fact, my M.Sc.-thesis-to-be (1975, I vaguely remember) was about implementing just such a billing system.