Why is cloud computing attractive to business? Well, if you consider storage, compute capacity, databases, payment processing and everything needed to run a business, it all requires a bunch of heavy lifting. It can stop your business if it breaks; yet it really doesn't bring any value to your customers. Nobody cares where a photo management site stores photos, but without that capability, the application breaks. So it's a lot of work, and a lot of exposure, yet there is very little payback. Not having to worry about that muck--being able to focus on product development, sales, figuring out your strategy, and so on--is a much, much better use of time for most businesses. So that's one big reason why there's so much IT activity trying to move into the cloud.
Source: Intelligent Enterprise, http://www.intelligententerprise.com