at this: "It would be interesting to repeat this analysis using Facebook data, but there is no reason to believe the results would be substantially different."
Yes, because the millions of smartphones out there with a camera and a Facebook app (as opposed to a flickr app) aren't going to skew the results at all.
Flickr is for people who like photography; ergo, the data is going to be skewed heavily towards actual cameras.
Facebook is for people sharing themselves with their friends and the world. One only has to peruse a random person's Facebook profile picture page to find hundreds of self-snaps taken in the bathroom, or at the pub, or on a train, or whatever.
Kodak, in my opinion, failed because they neglected to make quality products in their particular niche (easy to use, inexpensive, easy to share). They offshored their production, so Kodak cameras were notoriously hit-or-miss in regards to actually working right. They missed the highend market (then again Kodak was never known for that anyway), letting Sony, Pentax, Canon, and Nikon beat them there. They failed to leverage their gigantic photo paper experience into anything worthwhile (I own a Kodak printer that, as I type this, refuses to print due to some bizarre error I don't have time to diagnose).
In short, Kodak failed because Kodak fucked up. Photography isn't going anywhere. Hell, film photography isn't going anywhere. Kodak just stood still and let the world pass them by.
They took our Kodachrome away, and nobody cared.