Macworld had an article describing how to report problems with the Maps in IOS6. Apple hasn't gone out of their way to publicize this and it's real easy to miss in the app.
If you peal back the map layer, at the top and almost impossible to see given the color scheme (it's circled in red below) is a ink to report problems.
This opens this window:
Also there is another way to report errors about specific points that come up wrong. If you click the blue icon on the label that comes up attached to a pin you'll get this
Use this to report problems about the specific location that came up, wrong name, wrong business type, etc.