Forthcoming projects such as DES, LSST, WFIRST, and Euclid aim to measure weak lensing shear correlations with unprecedented precision, constraining the dark energy equation of state at the percent level and providing precision tests of general relativity. I will address several of the leading challenges to this program. Reliance on photometrically-determined redshifts constitutes a major source of uncertainty for these surveys. Additionally, interpreting the weak lensing signal requires a detailed understanding of the nonlinear physics of gravitational collapse. I will discuss the stringent calibration requirements on these sources of uncertainty, compare these requirements to the contemporary state-of-the-art in predictions of the matter power spectrum and photometric redshift estimation, and discuss strategies to utilize forthcoming data optimally.