I ran across this IDC chart on what customers want with cloud computing service providers. The survey is from August 2008 so it's pretty current.
Overall not so surprising that cost and performance are at the top of the list. I was a bit surprised that an established provider fell into a lower percentile. I guess that's mitigated by the #4 response, the ability to "move offerings back on-premise"; assuming that means being able to move data back on-premise. I would have figured that being an established provider would be more important.
A recent Information Week article on the closure of Goghead (a low-cost application platform hoster) highlights the risks of cloud computing, especially when the provider goes out of business. Still I guess if you're joining the cloud frontier you'd expect some risk. Even if it's a "large, established" provider there still are risks in the "how do I get my stuff back" area. As IW the article points out:
Choosing a stable vendor can reduce some of the risks of cloud computing. But even Google acknowledges that the migration path off the Google App Engine, should its customers want one, needs some work. "This is an issue, and we know it's not as easy as it should be," said product manager Pete Koomen.