[zbentley]

Well, there are teachers and there are teachers.

More specifically, some folks like to teach because it makes them feel like an expert when they're not. That's bad.

Some folks like to teach because it helps them learn-by-teaching and helps their pupils learn-by-questioning (and learn by questioning and receiving an honest "no idea/I might be wrong!").

The quantity that's in short supply is not expertise. It's humility.