Is re-appropriation missing?
As I see it, Fischer would have misled us by not explaining the dip in the adoption graph. The deviation from the (mostly exponential) upward trend is very interesting, and I'm glad that he examined it. However, the period of decline does not make the telephone a technological failure. The telephone is clearly a successful technology: it found a place in almost every American home by the 1970s. I wish I had a similar graph for radio during the same period, to see if a similar decline happened during the Depression.
Mengxiao Zhu's argument that Depression made farmers choose among competing technologies is compelling. I recently read the book Consumers In The Country. It argued that rural consumers (specifically) re-appropriated the telephone, automobile, electricity and housecleaning appliances in new ways. While I believed in most of Fischer's analysis, I was surprised that he did not talk about re-appropriation. Rural consumers could tinker with the car much more easily than the phone, finding new uses for it. The phone was largely a black box to a rural consumer, with the exception of the farmer running the coop. Rural consumers could and did find new uses for the automobile, like hooking a washing machine to the car's axle. So, I would speculate that since farmers had to choose between technologies, the car looked more attractive since it could be taken apart and put to new uses.