there's probably a limit of 16000 or so. but you'll hit a
performance problem long before you get 16000 movieclips on stage.
how many movieclips you can get on stage and have decent
performance depends upon the host computer system and whether you
have flash 8 and can benefit from enabling the cacheAsBitmap
properties of you movieclips.
the best way to find out how the number of movieclips will
affect your project is to run some project-specific tests.