The notion that an Amazon or Google has an inherent cost advantage in building infrastructure is plain wrong. This notion comes up over and over again in cloud computing discussions. Most recently on a thread where I responded in some detail. Recommend you start there and then as soon as you are finished head over to James Urquhart’s more detailed blog posting on the same topic: “Do Your Cloud Applications Need to be Elastic?”
Cloud computing is not a panacea and these are not the droids you are looking for. Move along. Move along.