They're right, too. Most of the PC universe is pure greenfield for virtualization vendors. It will stay that way because end users, for the most part, don't want to be virtualized. They don't mind if someone else manages their line-of-business applications and makes their storage available without too much hunting, and keeps the network attached and running.

But they don't want to have to dial in and stay connected while they're on the road, or working from home, or even be unable to load MP3s on their hard drive and play music in the office while they work (on headphones, of course).

PCs are like desks; everyone knows they belong to the company, but mess with your workers' desks and the personal stuff in them and you're in for a world of trouble.

That's why desktop virtualization will be successful on only a limited basis. It will remain attractive to the same kinds of companies for the same kinds of roles that use remote sessions and thin clients and virtual desktops and all the other ways to cheaply support PCs used by more than one person for relatively generic functions.

Call center operators, bank tellers, data-entry clerks, retail clerks and all the other non-knowledge workers who need to either plug information into a computer or get it back out, are good targets for virtual desktops.

Anyone who has to spend hours and hours in front of a computer and is expected to come up with answers to problems using their own imagination and experience, or use their brain as anything but a conduit for information from customer to computer, wants some control over their work environment.

True, VMware (and probably others) are now making arrangements to allow virtual desktop users to work offline. But that's just an extension of the partial-VM that I mentioned before. As they have with gMail and Salesforce and all the other selective-virtualization services, end users will accept the virtualization of some aspects of their working environment. And that level of virtualization will save some money and effort for their employers. It will be much easier to update applications that users access only through remote session on a secure server, for example.

Web front ends became popular interfaces for business applications for the same reason; users didn't mind going through a browser, and all the code sat on the server. No more wandering around userland with a DVD updating everyone's fat client every three months.