1. An event listening system, the event listening system comprising: a file system including a plurality of files, the plurality of files logically stored in a tree and including a first file, a parent file of the first file, and a grandparent file of the first file; a first data structure for the first file and configured to track a set of listening files, each of the listening files having at least one process associated with the respective listening file that is listening for events that affect the first file; a first data structure for the parent file and configured to track a set of listening files, each of the listening files having at least one process associated with the respective listening file that is listening for events that affect the parent file; a first data structure for the grandparent file and configured to track a set of listening files, each of the listening files having at least one process associated with the respective listening file that is listening for events that affect the grandparent file; and a traverse module configured to, in response to receipt of an identifier that is generated in response to an event that affects the first file: access the first data structure of the grandparent file; access the first data structure of the parent file; review the grandparent file's set of listening files to identify any listening files for the grandparent file that are also listening files for the parent file, but that are not being tracked by the parent file's first data structure; add the files identified in the review of the grandparent file's set of listening files to the parent file's first data structure; access the first file's first data structure; review the parent file's set of listening files to identify any listening files for the parent file that are also listening files for the first file, but that are not being tracked by the first file's first data structure; and add the files identified in the review of the parent file's set of listening files to the first file's first data structure.