Existing examples of a file compression schemes are visible in graphics programs for both the Atari and other platforms. The most famous Atari graphics compression formats are Koala-style (usually left-to-right) compressed graphics and ColorViewSquashed files (using a very similar algorythm).
In the PC/Mac community, GIFs, JPGs and many other graphics formats are compressed by their very nature as well. Of course, one can convert them into uncompressed images (like uncompressed Macintosh PICT bitmpas, Windows BitMaPs, etc.) but the files can end up being very huge.
Although huge files wouldn't be the major problem with Atari applications, one must remember that at times, drive space can be very limited, so a simple tokenization-based compression for text files built into a word processor (and being transparent to the user) could come in very handy!
If you have questions or comments on this, let me know!
nbs@sonic.net