Not to oversimplify this, but I'm going to anyway:
In order to have your tires wear evenly and achieve reasonable tire life, 2 things must be the case: the tires must be flat to the ground when the vehicle when the vehicle is driven and the tires must roll along the same line as the vehicle. Doing anything other than this and you will either a) wear the tires out on 1 edge first, and/or b) scrub the tread off the tire at an increased rate.
BMW sets aggressive specs for the vehicle because they expect it to be driven hard. If you are occasionally drag racing the kid down the street, but otherwise driving it to work, that doesn't count. If you live in the country with twisty road and occasionally you drive them at something faster than the speed limit, that doesn't count. If you are on a dedicated race track and are actively competing with other drivers for the fastest time, then THAT counts.
My point is this: For every mechanical device there are a certain set of use assumptions. Those assumptions drive the parts, design, and set-up after the fact. Deviate significantly enough from the use assumptions and the set-up parameters no longer hold. I run very little camber on the rears and get great tires life, but at the expense of being able to track my car. Since I don't track it, this is ok.
There is no one set of "right" specs for the car. There is a "Right" spec for YOUR car and YOUR driving, but not in general.
d-