In an application at work where we deal with mapping and geo-coordinate systems and stuff we frequently all sorts of fun little bugs because a point on the map doesn't know whether it's in geographic coordinates or in the current transformation system or in screen coordinates. They all use the same class and can be freely mixed. Alas, my suggestion of using different types to encode different coordinate systems was more or less ignored (too much effort cleaning up a 15 years old codebase).