Imho, "too much camber" is when the amount of camber > the amount of camber to benefit the handling of the car. I dont personally care for the look of an over cambered car, and would only run more than -1 if it improved the handling for that specific track/car. But thats just me.
For example, heres the most camber ive ever run
Was about -.6 i think, -2" springs, 19x8 +38 with 235 tires