Knife Throwing? One more step on the path of learning how to dodge bullets!!! Just like O'Sensei!
I was actually pretty darn good at this when I was six years old and playing cops and robbers..."I shot you!!! No you didn't!!! I dodged the bullet!"
On a more serious note... In a real fight unarmed... I will grab and throw anything to distract and close distance or to retreat depending on the tactical situation... but I would never ever "throw" a weapon at someone unless it is the very last resort. A knife is much better in my hands than in the hand of my opponent.
As Chris mentioned "household object" Randori is good to practice for awareness every once in a while.
William Hazen