The problem with the loss of a large piece of rotating mass is not the loss of lift (most rotors have enough collective pitch to give the remaining blades the angle necessary to make up the lost lift.)
The vast problem is the whirling imbalance, which is usually several times the mass of the helicopter. For a 10,000 lb helo, the blade might have 30,000 lbs of centrifugal force (physics jocks please forgive me) so that the loss of a blade can give you as much as 3 g's of lateral imbalance.
This is not just a pilot shaking problem, it is also a primary structural nightmare. The fuselage usually has a lateral natural frequency of about 3 to 5 Hz. To see this vibration on your helo during your next walk-around, try to shake your helo by grabbing the tail and giving it some tugs laterally. Find the natural frequency by shaking it where it "likes" the frequency and shakes a bit more, like "pumping" a swing to make it get higher. For many helos, this natural fequency is lower than 1 per revolution, so it can be excited by the big imbalance due to the loss of the blade. For larger transports, this frequency is the torsional-lateral tuning of the vertical tail and the tailcone.
If a blade is lost, the shaking can literally tear the aircraft apart, typically by collapsing the tail cone where it attaches to the fuselage. Look at this terrible video carefully, and note how each airframe failed in the same way, at the same place, long before the ground was struck:
http://www.thatvideosite.com/video/868