Phaseless auxiliary-field quantum Monte Carlo (ph-AFQMC) is a state-of-the-art stochastic electronic structure method for the study of strongly correlated electronic systems that seeks to recover accurate ground state energies and properties by repeated sampling of the imaginary time propagator. ph-AFQMC has been documented to perform well in the prediction of thermochemical properties of small organic molecules and transition metal compounds. In contrast to approximate density functionals, ph-AFQMC can predictively compute quantities such as spin-gaps and weak electron binding energies,. Recent algorithmic developments have enabled the accurate computation of properties other than energies. ph-AFQMC has also been documented to parallelize efficiently on modern graphical processing unit architectures, and localized orbital implementations (of reduced computational expense) have recently been reported. However, the accuracy of ph-AFQMC depends (sometimes sensitively) on the trial wavefunction used to constrain the random walk via the phaseless constraint. Many trial wavefunction forms have been used in the literature. The simplest choice is a single Slater determinant, using orbitals from, e.g., Hartree-Fock, Kohn-Sham DFT, orbital-optimized regularized MP2 methods, or self-consistent AFQMC schemes. A popular trial wavefunction protocol for molecules, especially for transition metal complexes, employs CASSCF trial wavefunctions. However, the exponential scaling of the cost to obtain these wavefunctions (with respect to the size of the active space) renders this approach infeasible for even mediumsized molecules, especially those that are strongly correlated. We note that while selected CI algorithms can reduce the scaling prefactor of active space CI calculations, and indeed very efficient algorithms exist to incorporate these into the ph-AFQMC framework, the exponential cost will still prohibit application to large chemically-relevant systems. Another important point is that size-extensive trial wavefunctions will be required for ph-AFQMC calculations of extended systems that must be extrapolated to the thermodynamic limit.