At times I do some accidental defoliation, and those lost leaves have always worked as a reminder to me why I normally save as many of the original leaves as I possibly can.
The side losing fan leaves always ends up with smaller buds for some reason compared to the corresponding side with the leaf still attached; coincidence right?! đŹ.
The only defoliation I do on purpose is the leaf removal very close to or just after harvesting to expose the colas for some sexy pictures.
I prefer to get rid of the leaves before the plant is dry, calling it wet-trimming. :)
The trimming phase before the buds end up in the curing jars is the only part of marijuana cultivation where I can go barbarian mode and just turn everything to BHO if things don't go 100% smoothly.
Buds has to be dense, nug shaped, high flower to leaf ratio, pref flowers stacked on top of more flowers; no sugar leaves at all or very little, mainly just dense flower-mass.
In order for this to happen defoliation is a big no-no and nutrients added are aimed at preventing the plants ability to create leaves in the buds and promote her to create flowers.
This is done by letting her have the old leaves still attached and also restrict the N in her food, using the fan-leaves as a marker for how much/little nutrients to administer, nitrogen in particular.
Very subjective, of course... if you are into mutilating the plants, calling it defoliation--you do you! Who am I to judge? :)