Why do SZ Blind Survey? Find SZ selected sample of clusters Followup in X-ray etc to do "single cluster" studies: Hubble constant, Gas mass fraction Joe Mohr yesterday Use number of clusters as function of redshift (and mass) to: Confirm LCDM paradigm! (non Gaussianity?) Further constrain cosmological parameters (w): Need a lot of clusters and hard systematics! Large redshift reach of SZ, and near-constant limiting mass advantages for both.