Interesting thread...the more I read Dan H. the more I agree with him. The below quote is from Sensei Takahashi's reply on the "Why do we turn our heads when pinned" thread...I think it speaks to the paradigm in which we train. IMHO, if someone is slamming you down when you are giving your body to them then something is wrong.
In Aikido especially, the nage is given huge leeway in finishing the technique, which would be totally unrealistic and unacceptable for the uke to yield to in an actual confrontation, and life or death situation. Thus the agreement that uke allows the nage to perform the waza thoroughly without real resistance, and that the nage accepts the responsibility of keeping the uke safe from any real threat of harm, is the basis for Aikido's kata form of training