Dips are more pre-disposed to producing dysfunctional mechanics than most upper body exercises. When performed incorrectly, dips will wreak more havoc on the shoulders than just about any other movement.
However, when executed with perfect technique and appropriate body adjustments, they're actually therapeutic on the shoulders. It's important to master the correct form in order to reap the worthwhile benefits while avoiding the potential drawbacks.
Scott Abel says that maximum load isn't the same thing as maximum weight and he wonders why most people don't get this. How much you can lift isn't the deciding factor; the deciding factor is how much stress a muscle endures.