If for some reason my files gets moved, then any reference to those songs in any playlist will get removed. I would much prefer to keep the entire playlist in tact and have it show "file not found" at the very least.
This way I can see which files are not found and rebuild it manually at the very least, instead of just having all my playlists wiped out.
What I tend to do is pour all my new music into an unsorted directory and then the files get moved upon sorting, I would love to be able to keep my playlists in tact during this process.