This is an interesting thread. With the exception of things digital and electronic, and societal insanity, I think just about everything that's been mentioned is something I knew by the time I was 15, in the 60s, from reading contemporary (non-esoteric) photo magazines and books, and it was considered stuff you needed to know if you were serious about photography.
Then when cameras started to have meters in them, and no one had to think or know how they worked--just center the needle, focus, and push the button, the magazines of the time started talking about how in the future anyone would be able to call himself a photographer without knowing a thing about photography.
I guess that time is now. I cruise Flicker, and I see 15 year old kids doing the most incredibly innovative stuff, and you know they probably don't know anything that's been in this thread.