I’ve known about reference movies for a long time, but I have never had the opportunity to use one before today. I am working on a project that is roughly 2k x 1k and uses a still sequence from cinema 4d. Final cut doesn’t really play very well with image sequences, so I used quicktime 7 to import the image sequence and export a reference movie. I saved a TON of disk space, and a fair bit of image quality as well, seeing as it doesn’t have any additional compression on it.
For the unaquainted: reference movies are basically a pointer that tells quicktime “hey go play from this file to this file” without actually copying the original source. If I were to share the ref movie without the source, then it would be useless. That is the reason why I have never wound a use for them before – they are easy to break, and it is usually much easier to just use the actual files.