Desktop Linux Sliding in Under the Radar?

Paul Johnson asks: "This article at ComputerWorld describes a sysadmin's discovery that many people in his company are installing Linux on their desktops without consulting IT. The writer is concerned with the security implications, but there is a wider issue. At present the 'official' penetration of Linux into the desktop market is something around 1%. The writer of this article doesn't give figures, but it sounds like he may have stumbled on several times that percentage of desktop Linux installations. If so then this is an important trend. Linux got its foot in the datacentre door in exactly the same way a few years ago, with unofficial installations doing odd server jobs. If you are a sysadmin, in an organization that runs Windows on the desktop, have you stumbled on many unofficial Linux installations?"