With subject location aware cropping active, if a user changes the subject location several times for an image to find the right position, each time new files are generated (with the subject coordinates in the filename) while the old ones are not deleted even though they are most likely no longer used anywhere else since those coordinates are now gone and replaced with new ones.
On a larger scale (multi-user setup, several sites, ...), this can easily take quite a bit of disk space and hit other problems.
One solution would be to use a cronjob to clean up the mess but not enough information would be available to the script to make a decision what should stay and what can be safely deleted (e.g. three files with different subject locations - which is the one to go?).
It would be nice if the subject location changes, the images with the last coordinates are safely deleted after the model has been saved.