  High Velocity Clouds (HVCs) have recently attracted renewed attention as
being long lived, massive dark matter dominated clouds of primordial
composition distributed throughout the Local Group. In this picture the HVCs
would contain a few times 10^7 M_sun of HI and would be at distances of a few
hundred kpc to 1.5 Mpc from the Local Group barycenter. If this extragalactic
interpretation of HVCs is true, similar clouds are expected in other galaxy
groups and around galaxies. We discuss the limits blind HI surveys and QSO
absorption line studies put on this proposed population of clouds.
