Hello!
I recently found this strange behavior. When you parent an empty (IK target of bone) to the base-bone of your armature and animate it. The empty cannot follow absolutely the movement of the base-bone. It causes nice motion.
Here is an animation where this bug/feature is used. The arms of the mech arent animated. Only foots and base-bone.
http://www.tuubi.net/jarkko.toijonen/duuni/mech_remodel_walk_yafray.mov
Could this be developed to maybe soft position constraint? …or something. Here is The Adam Scott´s demo reel. At the end he is showing some nice use of soft position constraints.
http://www.3dadam.com/media/full/AdamScott_DemoReel.mov
Thanks for listening!