dadaumpa:
Regarding pinMode(), that's curious. You mean it has no effect on A6/A7 because of their analog, input-only nature?
pinMode() has no effect on analog inputs (A0-A7).
When analogRead() is called, the pin switches to an analog input regardless of what the pinMode was set as.
dadaumpa:
Because the page http://arduino.cc/en/Tutorial/AnalogInputPins actually uses pinMode() on an analog pin.
Yes, because the code in that example is showing how to use the analog pin into a digital pin.