Users discovered this after successfully rooting their new G2s. They only realized after rebooting that their mods had been undone. HTC's enforced limitation, while unsurprising, is still a slap in the face to those who feel entitled to modify what they've purchased. This is particularly strange when so many are drawn to the 'openness' of Android.
HTC's is a similar but more aggressive anti-rooting measure than other companies have recently employed. Apple, for example, combats rooting in the form of iOS updates. Google goes so far as to retain the ability to remotely install and uninstall your Android apps.
Lauren Weinstein, a blogger, posits that the G2 "is using a firmware rewrite system to replace '/system' mods with the 'official' firmware upon reboot." Users haven't determined if rooting is completely impossible. If nothing else, the anti-rooting measure will present a new and interesting challenge to the modding community.
source: The Register via PPCGeeks