Frankly, I don't think cloud computing is the Next Big Thing people make it out to be. It's just another case of something the geeks have had for years (file servers, easy remote access to everything) being adapted to the mainstream. Sure, it's better for many, and the benefits to web and app hosting are significant, but "cloud computing" means roughly "on a server somewhere else."
Supercomputers in the cloud, and supercomputers (iphones/blackberrys) on our hips connected by high-speed ip based broadband lines will no doubt be significantly trans-formative in our lifetimes.