Mainly useful if you use Dropbox to synchronize MATLAB files across different computers.
DROPBOX keeps track of the location of your Dropbox folder across different machines and operating systems. On first-time use, it asks the user to locate the local Dropbox folder through a GUI window. The m-file then updates itself to recognize different machines through their hostname, so that only one copy of the file is needed (that you can keep in your Dropbox).
DROPBOX does not rely on MATLAB preferences so it is robust across MATLAB versions and after fresh installs.