I'm an engineer at heart. One of the hardest things that I have to do on a daily basis is to ask myself where what I think is cool conflicts with what the user needs. Or indeed if my cool idea will harm the user. As engineers we tend to focus on the cool bit. I too have fallen into that trap and I expect to do it many times in the future. But I try to be aware that this can and will happen.

I think asking language nuts (which isn't limited to those who write compilers, but also extends to practitioners with deep knowlede) to be aware of this is particularly important in that people look to them for enlightenment and advice -- and when they do harmful things it has a huge multiplier effect.