It would clearly be a different path than Elon's startups. But it's impressive that YC is willing to do the funding legwork for such an ambitious company, if they believe in it.
But PG wasn't an established authority back when PG was writing fast. I remember reading PG in 2006, and you'd read lots of snarks on the tech forums of the time (Slashdot, Digg): who is this guy, and why should we listen to this bored washed up multi-millionaire who sold his startup to Yahoo? He hasn't done anything of note in the past 10 years! (They said the same thing about Philip Greenspun too, who was also writing at a faster clip back then).
Look, at the end of the day, "established authority" is only loosely correlated with worthwhile meaning. At some point you're going to have to move past the author and evaluate the words on the page on their own merit.
MSR is only "R" (and that too only a subset of the total research that happens throughout the company - the stuff that can be classified as "basic science"/longer-term), the "D" happens all over the company in the various departments.
I can't answer your first question about why left-handed people exist, but I can provide some clues about the proportions:
Left-handedness is a disadvantage in society where everything is designed for the right-handed person. However, there is one advantage to being left-handed: in hand to hand or sword to sword combat, the southpaw has an advantage in being unfamiliar.
This article http://www.economist.com/node/3471297 (Economist, 2004) describes an empirical finding: in societies that were historically more violent, the left-handedness proportion is higher.
Perhaps this is also why left-handed people even exist. They have an advantage in historical person-to-person violent conflicts. This advantage would go away as their proportion gets higher. I presume (this is conjecture) that the minority proportion that it is, is the steady state equilibrium where the violent advantage outweights the other disadvantages of being out of sync with society.
This makes sense. Just as iTunes started cutting out record labels and making direct deals with artists, Amazon can do the same.
The real question is: how will Amazon go about replacing the work that, today, gets done in publishing houses? The biggest one I can think of is editing. But there are probably others that I'm not aware of.