Idiots.Twenty years ago, thousands of Germans converged at the Berlin Wall to watch as the hated barrier between east and west was torn down. But tonight, many fans hoping to catch a glimpse of U2 as they played a free concert to celebrate the anniversary of the historic event would have found a small obstacle in their way: a hastily erected wall.The organisers of the event, the music network MTV, erected a two-metre high "sight barrier" to exclude those without one of 10,000 free tickets...