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 used to have a similar setup -- SRAM Dual Drive 3 with a 10-speed 11-36T cogset with a single chainring -- but it was simply too much gearing, 19-120 gear-inches or something crazy like that. I got rid of it because it was plainly excess gearing at the expense of weight and complexity. Your friend is even worse with a double crank and FD. Just because you can doesn't mean you should. There's a lot of aspirational, Walter-Mitty-esque gearing going around.
Btw, the Sram DD3 hub has a torque limit. You can't run a big cog and too small a chainring with it without busting it.