However, if there are any schools champing at the bit eager to get some XOs for their schools, I only have one request for them. Please don’t tether them; let your students take them home. Don’t lock them down; encourage students try to run their own software and tinker with the operating system. Get them dirty. Make students collaborate and create stuff. Otherwise, the XO will be just a miniaturized desktop PC, a mere reference and publishing tool, and not the transformative device as was originally conceived.
This is not really a concern. What are the steps involved? Basically, take your XO, install some other conventional Linux distro (if that's even possible) and use that. The likelihood of a school in the US doing that approaches zero.
Perhaps you'll be able to put Windows on it someday. There will be cheap alternatives for low cost pre-installed and supported Windows laptops though. Schools won't want to bother putting Windows on their Linux machine any more than they want to put Linux on their Windows machines.
The XO as it ships will be a uniquely bad multi-user computer. That it is used by one student is a fundamental design principle. Of course, it will be possible to share, but it would be a lot more like sharing a cell phone than a computer, and it'll be quickly obvious that it doesn't work on any scale.
The thing to look out for is schools banning them, which will happen almost immediately. The question is whether the OLPC hype, education focus, and use in the developing world will expose this a being absurd in a way that other electronics bans have not. If it does, it just might open up some broader conversations about how locked down school IT has become.