All quotes below from: http://www.classicrendezvous.com/Italy/PMP_crk_ad.htm

From company ad: "The L-shaped design increased the pedal propulsion power and lessens energy dispersion on the downstroke."

"1981: Soviet Olympic team commissions study by East German Sports Academy to determine extent of functional advantage of new bent cranks. To cover bets, Soviet applied mathematician carries out extensive analysis (256 pp of equations) to optimize shape."

What I really really want to see is the Miyata/Shimano AX ersion of the bent crank arm:
"1984: Miyata introduces Shimano AX aerodynamic bent cranks with concave pedals to match. Availability is restricted, and interest is intense."

The 1984 U.S. Olympic team apparently wanted some of that snake oil, as they tried to get some of these cranks, but could not find funding (maybe b/c they over budget on the Huffy bikes.)

More really cool and bizarre crank designs here (check out the chainring with spokes for spider arms):
Bike Works NYC Chainring Archive