1. A computer-implemented buddy list pruning method, using a computer hardware system, for instant messaging system performance enhancement, the method comprising: comparing, using the computer hardware system, buddy list name entries in a buddy list to entries in a network directory used to authenticate users into a network supporting the instant messaging system; characterizing, using the computer hardware system, selected ones of the buddy list name entries as either invalid where a buddy list name entry cannot be matched to an entry in the network directory, or valid where the buddy list name entry can be matched to an entry in the network directory; performing, using the computer hardware system, presence awareness only on valid buddy list name entries in the buddy list; storing valid ones of the buddy list name entries in a valid cache; and, storing invalid ones of the buddy list name entries in an invalid cache.