so the story goes:
during the mayday holidays, a group of americans decided to go near mount everest and protest, campaigning for the independence of tibet. yes, so the chinese govt decides that they need to station people everywhere to check foreigners really strictly from then on, and require a guarantor agent and daoyou tourguide to follow these naughty foreigners (well, the visa is called an Alien Pass) everywhere they go. thus making free and easy tours of tibet near impossible. yay!