That and peak lateral grip occurs at some small negative dynamic camber. Grab an eraser and hold it perpendicular to a table. Push it to make it slide. Now tilt the top away from the direction of motion and repeat. You should feel it more difficult to slide. The same theory holds true for your tyres and the road.
The only real downsides to positive camber is increased steering effort and a higher proportion of mechanical trail to pneumatic trail (which means it becomes more difficult to FEEL the limit of traction at the front). Power steering takes care of the first one...
Don't forget that strut style suspensions typically reduce negative camber at the outside wheel in roll (as twilight mentions in the last post). Positive caster increases negative camber at the outside wheel.
I was going to say something else, but I can't remember what it was
ops: