Observations of large-scale peculiar velocities reveal that galaxies and galaxy clusters show coherent bulk flows—systematic bulk motion patterns—extending to distances of 250-400 million light-years, much larger than the scales on which bulk flows are expected to develop in Lambda-CDM simulations. These observed bulk flows are faster and extend to larger scales than theoretical models predict, suggesting either that the initial conditions of the universe are not Gaussian random as inflation predicts, or that large-scale flows develop through mechanisms not included in standard simulations. The existence and amplitude of bulk flows create tension with the isotropy and homogeneity assumptions underlying the cosmological principle and Lambda-CDM predictions (Feldman et al. 2010; Kashlinsky et al. 2012).