This all sounds rather fishy to me, and I'm still not convinced there is any real benefit outside of OCD-ness.
Forbidding things in stocks is a terribly inefficient and clumsy way to control what your workshops make. I find it a bit shocking that everybody seems to do this, actually. You can do the same thing with two actions per workshop only with a really simple fort layout, in a more intuitive and much more productive way... To set up:
1) Build your workshops around a central stockpile area depending on their theme. E.g. mechanics, craftsdwarf, and masons all around a central stone area. Set a stockpile in the middle to hold whatever you want your default stone material to be. For example, anything magma-proof perhaps (but any color, whatever).
2) make each workshop access this central area either immediately through a door, or down a long wraparound hallway that dwarves must use if that door is forbidden. So if you had exactly 4 workshops, it would be shaped sort of like a really fat swastika (I try to avoid having exactly 4 for this reason though =P)
3) Build another small room or two behind the workshop (or under it) with specialty stockpiles. For example, for my mechanics shop, I have a small (3x3) orthoclase and a small olivine stockpile, for color coded mechanisms that are magma safe. Each of these is separated by a door from the workshop and are closer to it than the middle area, if the main area door is closed.
4) To make green mechanisms, just forbid the door to the middle and open the one to the olivine. Done. To make yellow mechanisms, open the yellow door and close the green door... To not waste colorful stone, close the one you were using before and open the shortcut to the middle area. Always exactly two actions to make whatever you want.
The small stockpile size of olivine (3x3 or whatever) means that while my mechanic is working, haulers have time to go top off the stocks of olivine near him automatically, so he doesn't run out. You might want a slightly larger buffer if your worker works stupendously quickly.
Notice the NUMEROUS benefits over using the stocks screen: I can have my mason's shop producing only cobaltite tables, and my mechanics shop building only olivine mechanisms, and my crafstdwarves using only gray generic stones for pots
all at the same time. Using stocks would mean upwards of 200 different, unnecessary forbidding and claiming actions, and 1/3 the work speed. AND if I used the stocks screen, then my mason would have to run all the way down to my mines or wherever the hell I am keeping my orthoclase, for every item. This way, unskilled, idle haulers do all that moving right to him so he can be maximally productive, without me lifting a finger.
As for forbidding or dumping litter, it is vastly more precise and useful to use d-b-(c or f or d) and higlighting the pile of dead goblin useless crap on the ground wherever it is.
The only good argument I've seen here so far is for bars and blocks stockpiles, since that has a lot of things lumped into it, and it is indeed nice to know how much steel you have. Hardly more than a minor luxury, though, since your dwarves will immediately inform you with a big red message when you run out of steel.
But once you're making squads of full steel armor... you probably have a ton of idle dwarves anyway, so sure, crank up the bookkeeping. Early on though (<30-40 dwarves), I have more than enough for every dwarf to do all the time, and do not want to waste anybody to a 24/7 useless job.