The challenge with using Ubuntu for anything Enterprise is that the support group is limited.  How do you stand in front of your boss with no army of tech support behind you when the fit hits the shan?

“If you're building an internal or private cloud, Canonical wants you to use Ubuntu Linux 10.04 as your operating system of choice. To that end, the newest version of Ubuntu includes a feature set called Ubuntu Enterprise Cloud. In keeping with its open source pedigree, Ubuntu Enterprise Cloud is integrated with the open source Eucalyptus http://www.networkworld.com/slideshows/2009/110909-open-source-companies-list.html#slide4 private cloud platform, making it possible to create a private cloud with much less configuration than installing Linux first, then Eucalyptus.”

Link here.