You have to be a God in the Cloud
you are taking on everyone else's problems, and have to answer all the prayers.
Cloud computing is very interesting but don't believe the hype, it will morph into a facilitator not a be all and end all platform. A place to float to when your own systems go belly up, or you need to manage a flash mob.
There will be killer cloud applications, and search engines are already listed in that to an extent, Yahoo's move to open their search engine interface to unlimited use is a prime example.
But, you will still store stuff locally, you will still use applications locally. What is more likely is you computing platform will become more integrated into distributed computing, the clouds are just massive hubs and a way to coordinate that distributed computing.
With the Cloud we can see the ability to store and process in many different paradigms, some will make sense to do in a centralized location, others will not, really it is just improved integration. You should be able to deploy some new technology in unusual places that is very powerful, without having the powerful hardware in-situ.
The Cloud is the Borg though, and whilst that setup works for a lot of things, it would be dangerous to rely on it for everything, keeping some pieces of the jigsaw off the cloud, will probably be the way to finesse Cloud usage.