I have found two recent manifestos for clouds
a) “WE BELIEVE that clouds are unjustly maligned and that life would be immeasurably poorer without them”.
b) “it does not have to maintain multiple sets of artificially high levels of resources to handle peak demands”.
One statement is from the appreciation society of clouds and the other is an open manifesto statement for cloud computing?
open cloud manifesto security, data interoperability, data portability, and management are the main issues, although it looks like Microsoft are calling it for undue bias towards its authors.
From a security perspective Scott Bradner has an interesting twist on the “security nightmare” that comes with cloud computing.
As for rolling your own cloud …. have a look at Hadoop.