At the VMworld 2008 keynote there was an emphasis on vEverything, and in particular the vCloud.  At the high level, the idea is a great one, be able to seamlessly move workloads in and out of the Cloud, no matter where the resources exist in the cloud.  My datacenter, your datacenter, their datacenter.

In my previous life I was lucky enough to work on the team at IBM that was engaged in the beginning of the TeraGrid project.  A great project with a goal of uniting several academic HPC Cluster sites across the US, so they could share the computational resources.

We thought the biggest challenges would be of a technical nature, turned out the political and trust challenges far outweighed the technical.

How can I trust my data is secure at your site ?  Who will have access to the data ?  I need admin rights on your site.  How do we charge back for your hogging all the bandwidth with your project ?

I would encourage Paul Maritz to meet with the leaders of TeraGrid and discuss those challenges and how they deal with those issues.  It's the natural order of the world for us to learn from academia.