When I was programming an Arduino last year I ran into a painful programming halt when working with a color sensor. The color sensor was hooked up correctly (3 pins is not so hard...), but for days I could not figure out what was wrong with my code.
Would questions that are nearly completely about programming belong here? Normally you might want to post it on stack overflow but if it's using Arduino syntax, and robotics related external libraries, does it belong here?
The problem I had above turned out to be the external library using serial and screwing up the serial data stream that my code was outputting. A normal programmer wouldn't have been able to figure that out, but one who programmed robotics probably would be able to.
This specific example shows how blurry the lines can be between a programming SE and this one, where do we draw that blurry line?