I wrote a pretty darn lengthy article conveniently titled “How to increase the frame rate of your flash movies” and it has been published as the cover story in this months issue of the MX Developers Journal magazine. It is online to read for those of you that do not subscribe to the print version of the magazine. It explains Bitmap Caching, Memory Usage and scrollRect Panning in great depth and also contains some tips & tricks 
Check it out.
[p.s] 100 * 100 != 1000 - Typo in the article [/p.s]