This is a good discussion. As for as deadlifting without specifically training for it Ross Enamait recently pulled 495lbs.
He is obviously very string, snatching a 125lb dumbell, doing glute ham raises with multiple weight vests, pistols with additional weight.
I recently finished three weeks of heavy (for me) deadlifting, maxing out at 270lbs x 2 at a BW of 160lbs. I know its not much weight, but its the most i have ever done. I have trained the lift sporadically here and there, but never with much consistency. Before this i was doing Ross's 50 day program from Infinite Intensity. I am going to switch out my max effort exercise to something else for a few weeks, but i think i can hit double bodyweight by early next year. At 270lbs one of the limiting factors seemed to be my grip.