Earlier quoted context omitted.
True. >> "...and pay by the hour" If you have money to burn.
Being able to pay by the hour massively, massively reduces the capital expenditure required when launching a public site? You can launch on a relatively cheap $75-$150 a month and then if you get Slashdot/Digg your code can automatically scale and only pay for the extra capacity when you need ... that's kind of the point of the service. Check out Bezos at startup school last year talking about animoto : http://omnisi…
I can see the case for this sort of scalability if your traffic is wildly unpredictable - eg 1 visit one day, 100,000 visits the next - but I think that's rare.