If your Xbox has the Xbox-Live "feature" wherein the device connects to the Intenret on your behalf, be warned: Xbox-Live will "update" your box to "fix bugs" without your permission or knowledge. Included in the "bugs" that will currently be fixed by Xbox-Live is the "bug" that allows the device to run Linux.
The particular bug that this update will correct for the user is the ability to run Linux. Once the update is in place you will not be able to install Linux on your Xbox any more, at least not in the convenient way that the Dashboard bug allowed, according to the XboxLinux pages.
(via Hack the Planet)