Since the early 1990’s, steady progress by both observers and theorists has led to weak gravitational lensing becoming the premiere tool for mapping the amount and distribution of dark matter in the universe.  The upcoming European satellite, Euclid, NASA’s (hopefully) upcoming WFIRST satellite, and the Large Synoptic Survey Telescope (LSST) all have measurements of dark matter masses via weak lensing as cornerstones in their primary science goals.  It’s hoped that, over distances less than about 10 Mpc, the observations that result from these telescopes will enable astronomers to constrain the dark matter mass density of the universe to a remarkable, and truly unprecedented, accuracy of less than 1%.  In this talk, I’ll cover the basics of weak lensing and the way in which it is typically used to obtain dark matter masses.  I’ll also discuss a number of complications that, if not accounted for correctly, will make it exceptionally difficult to reach the hoped-for accuracy of 1% accuracy in dark matter mass measurements from Euclid, WFIRST and LSST observations.