1. A method of classifying computer objects, the method comprising: receiving from a tagging application and storing to a tag database, by at least one computer device, tag data for a first computer object, wherein the tag data comprises (i) an indication of a tag comprising at least two nested categories describing the first computer object, (ii) an indication of the first computer object, (iii) an indication of a class of users authorized to view the tag such that users within the class are permissioned, by a first user creating a new tag, to search for the newly created tag, wherein the at least one computer device comprises at least one processor and an associated memory, and wherein the tag database is in communication with the at least one computer device; updating, by the at least one computer device, a hierarchy of categories for computer objects to include the at least two nested categories describing the first computer object; receiving, by the at least one computer device, an indication of a first category selected by a second user from a graphical representation of at least a portion of the hierarchy of categories displayed to the second user; and causing a display of an indication of a plurality of tagged computer objects falling within the first category to the second user, wherein for each of the plurality of tagged computer objects, the second user is associated with a class permissioned to view a tag associated with the tagged computer object; receiving, by the at least one computer device, a subscription request associated with the second user, wherein the subscription request comprises a description of a third user, a description of at least one tag and at least one potential action to be performed on the at least one tag by the third user; and sending, by the at least one computer device, a notification to the second user upon the occurrence of the at least one potential action performed on the at least one tag by the third user.