I have to say I might agree with the Dante theory of KP Growth.
It is increasing at an alarming rate because more images are being defined as KP: baby bathtub photos, artistic nudes, sexting self-shots even if they aren't nude or explicit (possibly also de-contextualized socnet pics, I suspect), non-nude models (both as in "Webe" and as in "store catalogs"), and so on.
When you expand the definition of something, obviously the set size of what that something is defining increases.
Like you, I find no reason to suppose that KP, rigorously defined, is increasing at any rate significantly above the increase in all media online.
(There you have a confounding variable; since the technical barriers to production and to online distribution are already low, and keep lowering, even KP rigorously and narrowly defined should be increasing all other things constant, by technological change alone. Same as "legal" kiddie or non-kiddie material on youtube and flicker are still growing. Still, "an alarming rate" tells the story that they are growing significantly above the growth of legal media - and that's where I find no other explanation than the Dante theory)
Cuteness is to die for
Cuteness cannot fail
Cuteness knows no limit
Cuteness will prevail