34. The non-transitory computer readable storage medium of claim 25 , wherein the globally unique identifiers are URL fingerprints.
25. A non-transitory computer readable storage medium storing one or more programs configured for execution by a computer, the one or more programs comprising instructions for: partitioning a set of monotonically ordered document identification tags into a plurality of segments, each segment associated with a respective subset of the set of monotonically ordered document identification tags; subdividing each of the segments into a plurality of tiers, wherein each tier is associated with a respective subset of the set of document identification tags, and wherein the plurality of tiers are monotonically ordered with respect to a query-independent document importance metric; receiving query-independent information about a new document, the information including a value of the query-independent document importance metric and a globally unique document identifier for the new document; selecting, based at least in part on the globally unique document identifier, one of the segments; selecting, based at least on the query-independent information, one of the tiers associated with the selected segment; assigning to the new document a document identification tag from the respective subset of document identification tags associated with the selected tier, the assigned document identification tag not previously assigned to any of the documents in a collection of documents; repeating the receiving, selecting a segment, selecting a tier, and assigning, with respect to one or more additional new documents; and wherein the assigned document identification tags are assigned to documents in the collection of documents having globally unique document identifiers associated with the respective segment.