Obviously, Microsoft has a significant interest in making sure that users of the new breed of netbooks and MIDs hitting the market don’t get too comfortable using Linux. Many manufacturers have taken to installing various flavors of Linux on these devices to minimize footprint, improve performance, and reduce costs on low-power, low-margin hardware. Similarly, most modern Linux distributions provide features that are tough to find on Windows XP (especially XP Home); Vista clearly isn’t an option on these little guys.
ULPCs come up a lot in Ed Tech, partly because the OLPC XO, largely credited with creating this market, is an educational tool and also because ULPCs have the potential to make 1:1 computing realistic (or even to simply make any sort of computing realistic in developing markets). The OS of choice for students today will be the OS of choice in business tomorrow; hence, Microsoft’s concern over the use of Linux.