I'm rolling up my sleeves and trying to tackle the fundamental concepts of cloud computing for the first time. I am planning to build a highly-scalable web application, and can't ignore the potential benefits of cloud platforms. Now I think I get all the basic concepts of it, except when I try to compare it to service plans offered by traditional web hosts such as GoDaddy. GoDaddy, for instance, offers a Grid Hosting package where you can basically keep adding machines to your plan as demand grows.
How are plans like this different than a "true" cloud service offered by someone like Amazon?