Interesting thread. I had a brief look at the original Scrypt paper (which is quite old), but it was not obvious to what is meant with making memory intensive tasks more expensive. I'd like to see this quantified using numbers with today's memory technology. In addition it was even stated in the paper that one of the limits were based on 2-dimensional memory ingots, which we know will change in the next couple of years, to become 3-dimensional blocks of some electro-optical substrate. This is will have to effect of increasing memory size with x³ instead of x² for the same price. Now, if there's another way of mining that we could think of, that could avoid the mining growing pains into adulthood, that would be very interesting.