It works with the 1.3.10 PC version. You need to wait until they've put the quiver away, so wait until they're not practicing or until they're asleep - just enter the barracks at night and give everyone in there 1 daedric arrow. You will harvest many more than that on the next day.
Oh! Cool, I didn't know about this one! Do I have to take their own arrows away? And then just reverse pickpocket one arrow to each guard? Then once they practice, I pick up the arrows from the targets? or by pickpocketing again? LOL
So far I've only found 1 Daedric Arrow and even the Ebony arrows are scarce at times. The Fletcher in Whiterun has the most Ebony arrows for sale usually. Why the Fletcher in Solitude has usually none, is beyond me. Why can't Fletchers just sell 500 of each arrow, and a few bows... I mean they ARE Fletchers!
@ cobrasno1: I know you can summon atronachs and make summon atronach scrolls, but I highly doubt you can make arrows at that forge.