Wow, what gratifying points. First of all I am always thrilled when I discover that my tech speculation actually has some solid precedent in code! Full disclosure: I did spend some quality time with FQL myself, though happily as an explorer rather than a coder, so that author/post ID relationship may have been lodged in whatever part of the brain handles subconscious musings on social APIs.
And your point about the social graph relationship to my content vs NYTimes content (or whatever) makes TOTAL sense. I wonder if there would be some way to measure and map that — seems like it would be hard if not impossible, since Facebook doesn’t really pull friend data anymore, and I can’t imagine how you would know which friends had seen content you shared from multiple sources. Still, if we could figure out a way to do that, it would be fun to look at — I’m always fascinated by the intersections of different, apparently unrelated social circles who are nonetheless sharing the same content.