Consumer research has shown the downsides of offering consumers too much choice and is now starting to explore moderators of the effect of assortment size on consumer decisions. Building on previous studies, this research examines two side effects of tyranny of choice in the marketplace: high assortment entropy and high density of attribute values. We analyze two supermarkets—one offering small, the other large assortments—to examine how size, entropy, and density relate in the marketplace. We find that larger supermarket assortments come with higher density and higher entropy. Simulations of various choice strategies in these marketplace assortments reveal that making selections from large high-density and high-entropy assortments is time consuming, and better choice quality is not a forgone conclusion, even for customers with ambitious aspirations. © 2009 Wiley Periodicals, Inc.