This question is most commonly asked by people who are in the process of growing out thier hair. This is because,

The average hair loss per day with any length hair is 80-100 hairs per day

** The longer your hair is, the more it will get caught up in itself during the day and only come out as a "handfull" when you wash. This is especially true if you have curly hair or if you use a lot of holding products.
** 80-100 long hairs are double or even triple the hand-full of 80-100 short hairs.