That's a bad idea if what you want is to offload your email or other relatively commoditized software, as many small- and mid-sized businesses do.
It's an absolute requirement if you're primarily after the higher skills, uptime, management, flexible capacity and other advantages of apps running in the cloud, but have customers (consumers or employees) who won't put up with outages or slow performance.
If your audience is demanding, no matter how high the quality of the platform, they won't be happy unless you are there personally making sure everything is running the way it's supposed to.
In cases like that, though, at least putting demanding apps in the cloud means you'll have more help than you would if all the support and capacity and performance and security were up to you and whatever limited resources you can command in a data center designed to support only one company, and do that for as little money as management could possibly get away with paying.
Here are a few more detailed guides that may also help:
Gartner guide to getting the most out of SAAS and Cloud (presentation)
Do the risks of cloud computing outweigh the benefits (Risk Management Monitor)
Cloud computing for non-technologists: predictions and primer (Forbes)
Cloud computing primer (book review, click PDF at bottom)
Amazon Web Services -- economic, technical and usage guides
VMware guides to private, public clouds, self-service, openness, automation and management