The Collaborative International Dictionary of English v.0.48:

Exclusiveness \Ex*clu"sive*ness\, n.
   Quality of being exclusive.
   [1913 Webster]

WordNet (r) 3.0 (2006):

exclusiveness
    n 1: tendency to associate with only a select group [syn:
         clannishness, cliquishness, exclusiveness]

Moby Thesaurus II by Grady Ward, 1.0:

69 Moby Thesaurus words for "exclusiveness":
   Jim Crow, airs, alien, apartheid, arrogance, clannishness,
   clanship, cliqueyness, cliquishness, cliquism, color bar, contempt,
   contemptuousness, contumely, denominationalism, despite, disdain,
   disdainfulness, disparagement, division, esprit de corps,
   ethnocentricity, ethnocentrism, faction, factionalism, foreigner,
   hauteur, insularity, insulation, insult, isolation,
   know-nothingism, narrowness, out-group, outcast, outsider,
   parochialism, partiality, partisanism, partisanship, party spirit,
   persona non grata, quarantine, race hatred, racial segregation,
   ridicule, scorn, scornfulness, seclusion, seclusiveness,
   sectarianism, sectionalism, segregation, selectiveness,
   selectivity, selectness, separation, sniffiness, snobbery,
   snobbishness, snobbism, snootiness, snottiness, sovereign contempt,
   stranger, superciliousness, tightness, toploftiness, xenophobia