Too much empty cloud talk - we need to start classifying clouds, think what are they good for and start using them.
Amazon EC2, Rackspace, GoGrid, number of others are in fact IaaS - infrastructure as a service
Clouds like GoogleApps, Azure or Force - PaaS - platform as a service
IaaS vs. PaaS are totally different animals. Practically speaking, from a business perspective, I am very skeptical about generic PaaS (like GoogleApps or Azure).
Serious business users would use IaaS clouds due to it's scalability and procurement benefits, but who (in it's right mind) would have resources to start rewriting existing applications to run under Azure or GoogleApps?
I understand a young developer who would like to develop something for PaaS, but let's say this small development becomes a growing successful website - Can it be run under PaaS - what I hear in the industry today is "no way".
For example, DBAs complain a lot about SQL Azure Database, it's backup issues, scalability and visibility issues when it comes to problem root cause analysis.
From an economical perspective - also, no way, - right now, running fast growing web site on PaaS is too expensive and moving from it would be a pain.
As a note - I do see a great future for a specialized PaaS, such as Force - in this case, it is based on a solid and thriving existing community of business users with clearly defined needs and ability to pay for a right solution.
It would be great to see a PeopleSoft clouds or SAP clouds, but right now it is too far in the future.
I am an active cloud user and will share more about my practical cloud experiences. My company (Enteros) created white papers together with IBM about cloud scalability (which is also a big and misunderstood issue).