As conehead points out, as long as you're not using gif, jpg, or png graphic images, then it's easy to change the size of the movie by changing how the movie is presented. However, if you have any of the above image formats in your movie then changing the size dynamically will also affect the quality of the images because they don't lend themselves well to size changes.
So I guess the answer to your question is No, and Yes. It all depends on the content of your movie. I have never had the luxury of creating a movie that didn't incorporate these types of images so I've always made two movies - one for screen resolutions of 800x600 and below and another for 1024x768 and above. It's not that complicated or difficult to do.
I have had the opportunity of having to create several small swf files and load them dynamically as needed. THis is a bit of a challenge but one of the best ways to create a large presentation any yet still allow reasonable load times. This is mainly done for "all flash" web sites and I've found that such things as "About Us", Contact Us", Privacy Policy", and "Legal Issues" pages are rarely called and these are the ones that lend themselves well to external swf files. The same is true if you have a photo gallery or have large, hi-resolution images, or lage volumes of text. Rather than embed them in the swf, it's easy, and faster, to load them as needed.
There's always a better way. The fun is trying to find it!