The German Stare

One of the things I've noticed about German people is the stare. When I'm in a bus, or the train or in public I notice people staring at me. Once you notice people staring at you and look back, they keep right on staring. They don't smile or look away, they just dead stare you back. In the US I was always taught that staring is rude. I can't just death stare someone and keep a straight face, but apparantly Germans can.