1. A computer implemented method of membership list management, comprising: executing a set of rules, by using a processor of a computer system, to create a computed rules-based membership list; associating the computed rules-based membership list with a node in a hierarchical structure based at least in part upon the set of rules, wherein the hierarchical structure comprises a plurality of nodes, the plurality of nodes associating with a plurality of membership lists; caching the computed rules-based membership list in a membership cache for retrieval in response to a later request for the computed rules-based list; modifying the computed rules-based membership list by accessing the computed rules-based membership list that has been cached instead of executing membership rules to build a modified membership list; modifying a hierarchy of the hierarchical structure, wherein modifying the hierarchy comprises: receiving a rule change request comprising modification to a rule in the set of rules; determining whether the computer rules-based membership list is a membership list affected by the rule change request; determining whether the hierarchy of the hierarchical structure is affected by the rule change request; changing the hierarchy of the hierarchical structure by adding or removing the node in the hierarchical structure based at least in part upon the rule change request; and storing the computed rules-based membership list in a volatile or non-volatile computer-usable medium or displaying the computed rules-based membership list on a display device.