The following definition is taken from Wikipedia.org Here.
In computing, Desktop Virtualization involves separating the physical location where the PC desktop resides from where the user is accessing the PC. A remotely accessed PC is typically either located at home, at the office, or in a data center. The user is located elsewhere, perhaps traveling, in [...]

I recently found the following Cloud Computing Vendor List while researching the web.

Cloud Vendor
Level
Type
Status
Cloud Provider
Notes

3Tera
3
Server
Provider
Backbone
3Teras host solutions and provides software for other host providers

Adobe Air
1
Application
Not a Provider
Backbone
Desktop play

Akamai
0
Server
Not a Provider
Software Based
CDN

Amazon EC2
2
Server
Provider
Backbone

Amazon S3
2
Storage
Provider
Backbone

Amazon SimpleDB
2
Database
Provider
Backbone

Apache CouchDB
2
Database
Not a Provider
Software Based
IBM is involved

Apache Hadoop
2
Database
Not a Provider
Software Based
Hadoop is white-hot OSS enterprise search technology.

Areti Internet
0
Application
Provider
3Tera

Box-Net
1
Storage
Provider
Backbone

Cassatt
0
Server
Not a Provider
Software Based
Utility [...]

I found this website
Green Data Center Blog: Who are the Energy Hogs in Data Centers? where the author is talking about energy hogs in the datacenter arena. It would be interesting to know.
I would think those utilizing some form of virtualization technology would hopefully not be on the list.

Just read this article today on Grid Today which talks about a company 3Tera who offers scalable grid technology that is affordable to people at a level that was never before possible.
The Applogic Technology allows people to utilize a GUI interface (within a web browser) to create Virtual Datacenters.

Utility Computing, is also known as on-demand computing, or cloud computing. A Great Definition from wikipedia.org is as follows.
Utility Computing (also known as on-demand computing) is the packaging of computing resources, such as computation and storage, as a metered service similar to a physical public utility (such as electricity, water, natural gas, or telephone network). [...]

Right now there is a huge push to spend less on resources, and datacenter costs, as well as overal IT expenditures.
We in the IT sector have the ability to directly affect not only our end costs and bottom line, but the energy issue and crisis that our planet is facing today.
Here is an  article [...]

Below is a recent interview from CMO, John Pozadzides from Layered Technologies, Inc discusses grid computing, managed hosting, and dedicated server hosting.

Cloud Computing Leader 3Tera selected for innovation, value and enterprise-readiness
of its award-winning AppLogic™ Cloud Computing Platform
Aliso Viejo, CA – April 20, 2009– 3Tera®, Inc., the leading innovator of cloud computing technology and utility computing services, announces that it was named to the first annual listing of the InformationWeek Startup 50, revealed today in InformationWeek [...]