1. A method for extending metadata related to stored data objects within a data storage management system based on user-specified classifications, the method comprising: automatically obtaining metadata related to one or more data objects, wherein the data objects are stored within the storage management system; automatically storing the obtained metadata in a database of metadata; receiving a search from a user, wherein the search includes certain criteria related to the metadata; querying the database of metadata based on the received certain criteria; providing to the user a list of a subset of the data objects based on the query of the database of metadata; receiving data classifications from the user for associating with the subset of data objects, wherein the classifications are not stored at least in part with the data objects themselves; and associating the classifications received from the user with at least some of the subset of the data objects in a searchable classification index, wherein the received classifications categorize at least some of the data objects in the subset of the data objects within the storage management system.