Meta: on Supernatural

Mostly, I've been thinking about canon and fanon (or canon vs. fanon).
I'm very much intrigued to witness how little canon details get used, transformed, enhanced or ignored by writers (and it can be for a million reasons, of course, for ease of writing, for not remembering it, and what have you). I don't mean these observations as critical in a negative way, I'm just observing (I'm probably the first to tweak details to my own liking :), but as I said, it's fascinating to see how fanon builts on itself from writer to writer.
Also, spoilerish for the season finale.

( Randomly, SPN thoughts behind this cut )