http://video.google.com/videoplay?docid=2238323060735779946
This is the video that was posted when the Buffalo crash occured, in the first 6 minutes or so it explains the issues of tailplane icing and ice acretion on the tail can be significantly more than on the wing. If seen on the wing, you can be pretty sure more is on the tail. Once flaps are extended, nose pitches down and force required to get the nose back up can be dramatic. 400 lbs in some cases as stated in the video.
Of course it sure doesn't help that they were in icing conditions and not paying attention to the aircraft or that the PIC didn't have the best record in the first place, a sterile cockpit could have saved many lives in this situation.