First iPodSubwayMaps.com got shut down simply for too much traffic, then cities like New York and San Francisco sent poor William Bright, the app's creator, cease and desist letters. After that, New York at least offers the guy the ability to purchase a one year license to use their maps for $500.
But wait, there's more: just yesterday the Washington DC WMATA sent William a license to use their maps - for free! How cool is that? This is such a great gesture from a company in the day and age of "cease and desist everything." Like William says on his blog: everyone go to DC and ride the metro!