http://deli.oreilly.com/tmp/tmpAaaX_Efferent geographical areas, you can move your content closer to the people who are using it most. If an application is heavily used in Asia, have an instance running in a data center located there. This kind of flexibility may not be available to you if you have to own all the hardware.
Another advantage to the cloud is that it's a pay as you go proposition. If you don't need it, you don't have to pay for it. When demand is high, you can scale up, and when demand is low, you can scale back. Yes, by moving applications to the cloud, you're giving up some control and autonomy, but you're also going to benefit from reduced costs, increased flexibility, and scalable computation and storage. The Windows Azure Architecture Guide shows you how to do this.