This is what I found:
In FP 10, bitmaps are no longer restricted to a max size of 2880x2800. Now
they can be 4096*4096 with a max of 8192 for any dimension.
Flash authoring has always, and still, restricts the stage size to 2880x2880.
You've probably noticed the ability to have stuff offstage is cool for tweening like this http://www.cybermountainwebservices.com/
Thanks, but I'm not talking about the published stage size (in "Document Properties"). Im talking about the area you have to draw in while in authoring mode. It looks to be a little bigger than 6400x6400. Even if you manage to get something outside this area visible (I've been able to do this by zooming in and out) you can't use any drawing tool outside of this region (the cursor just remains an arrow).
This restriction doesn't make any sense to me though, since you can still move objects outside of this region.
The other limitation I was questioning was the size of shapes & MovieClips. If you try to make a really huge rectangle by manually entering the width & height, you'll get the "invalid size & position" error. However the Transform Tool does not enforce this limit - you can make things as huge as you want.
So why are there these loosly enforced limits that can easily be broken yet still make authoring large objects a huge pain? I wish Adobe's documentation had some discussion of them.