A friend of mine has a DAHON JetstreamEX fitted with SRAM DD3 rear hub, 10s cassette plus double crank, so he has 60 speeds. He is so smart that he can manage gear shifting well. I would need a computer to know which gear I should shift to!
I could see the value of that setup. Most of the time, running in middle range, so direct drive on the rear hub, more efficient and less wear. With the fat seat tubes on these Dahons, it's difficult to do a 3X crank, so when needed for heavy loads or steep hills, they have the low range reduction. The small wheels limit top gear, so when needed for a fast downhill, they have the high range overdrive. I can definitely see the appeal for full range of gearing.