An amusing anecdote from the Economist:
One particularly egregious regulation forbids flight crew from mentioning any landmarks the plane might be passing over (as if terrorists make plans that rely on announcements from the flight crew.) The "don't mention the Grand Canyon" rule is particularly breathtaking in its stupidity. After all, there's nothing to stop a terrorist from using a combination of pre-flight Google Earth prep and advanced in-flight window-based technology as a substitute for a helpful flight attendant.
A colleague who just flew from London to DC emails about the practical implications of this rule: Airlines aren't supposed to show that map thing anymore, so you can't track your progress across the Atlantic, and they don't tell you how long you have left in your journey. My neighbour, in the window seat yesterday, flagged down a stewardess to ask whether the land below us was Greenland, the stewardess told him that she wasn't allowed to tell him anymore!