OK, so in the process of commenting on Nick Carr's post, "The techno-utility complex", I came up with a term I like: cloud lock-in. This goes to my earlier conversation about vendor lock-in in the capacity on demand world--aka cloud computing. I like the term because it reinforces the truth: there is no single compute cloud, and the early leaders in the space don't want there to be one. Rather, they are hell bent on collecting your dimes every hour, and making it damn expensive for you to move your revenue stream elsewhere.
My advice stands: if you are greenfield, and data security and access are less of an issue for you, go for EC2, the managed hosting "cloud bank", or the coming offerings from Google or Microsoft. However, if you want to take a more conservative approach towards gaining the economic benefits of utility computing, make your own cloud first.