It's pretty much impossible to give a definitive answer to whether this is bad or not. I see the same thing happening--while my hair is long overall, 90% of the hair I shed is very short compared to the length of the rest of my hair. It could be that these hairs are breaking off, or it could be that these are miniturized hairs that are at the end of thier growth phase. It could possibly be that these are miniturizing hairs which are shed while on proscar because the miniturization process is reversing. It could be something else completely. I haven't read any reputable scientific research as to why this happens, these are just my guesses. But I wouldn't worry about it too much.
