I know at least one person who reads exclusively with cards that fall out... it can take a long time to get a decent amount of cards for a spread :P since she just shuffles and shuffles until she feels enough have fallen.  I sometimes do super-fast "readings" for my self just by shuffling my deck (taking sections and moving them to the front, since my deck is too big to shuffle easily any other way) and seeing which cards show themselves during the shuffle.  After about 7 cards I get pretty much the whole story.  If a card falls out when I read for another person, I try to just snag a glimpse of it and incorporate it into my explanations of the other cards-- it gives me an added bit of info about the person's situation, and I treat it as something that is on their mind but that they wouldn't necessarily decide to tell me on their own.

Falling cards do tell us to pay closer attention.
I usually keep them aside and make them (or it) an integral part of the reading. I keep it on the side and if I was doing a seven card spread, I still lay down seven cards and keep the fallen card close by. I usually try and see the fallen card as the querent's current state of mind or affairs.

I just think of the falling cards as specific things that thecards want you to look at or understand, things that are important whether you know understand it right away or not... =P

I just put it off to  my clumsiness I have never thought to read it, i will give it a try the next time =)

I always have a look at fallen cards, they tell me that i need to know something important and have a message to pass to who ever i am reading for.