I'm at Cloud Expo this week, and have been speaking with a great many people who are building their first clouds...public, private, and hybrid. Some are working, some are not. Here are 3 reasons that clouds are failing.
Reason 1: No governance. You need to have a good governance and management strategy in order to effectively operate clouds to support the services levels required. This means that governance software is monitoring your infrastructure as to set policies. Guys like Abiquo, and a few others, should be considered to address the management and governance requirements.
Reason 2: No performance modeling. While clouds seems like they should scale by some decree of the buzzword law, the reality is that most clouds are not optimized for performance or scaling. Make sure to model performance and scalability, and validate that the architecture and technology is optimized.
Reason 3: No talent. The largest issue around the failure of some clouds is the lack of architectural understanding of cloud computing, and the lack of skills required to scope, design, deploy, and test a cloud...private, public, or hybrid. Not sure I have a fix for this, other than make sure to get the expert help you need. It's relatively cheap considering the cost of failure.