From drifting in general, negative camber is going to wear the tires unevenly because less patch is actually touching the ground. As far as the camber degree, that's really going to depend on what type of tires you run. Some tires (again, this is more general drift FYI) are set up for diff degrees of negative camber. I beleive the Yok tires with drift rings are set to be cambered at a particular degree. There's enough grip for controlling your drift, but enough slip to have fun sliding. I guess it really depends on your tire.