I am building one to feed my pot bellied stove. I have plenty of big wood, but it seems silly to take big wood and break it down into small wood just to fit inside my stove, when I can take small wood (under 4 inches in diameter) and chunk it into wood to fit inside my stove instead. I have plenty around the edges of my fields, and land that I am clearing from forest into fields.
I have already built a feller-buncher head for my log trailer to make my firewood process 100% mechanized. It is on a micro-forestry scale, but it is 100% mechanized. I just have to build the chunker now.