In Type IIB string theoretic models of the early universe, inflation may be driven by the motion of D-branes in a warped throat region of the compactification, or by the motion of light geometric moduli as they are stabilised by fluxes. All of these models generically contain U(1) vector fields that arise on the world-volumes of D-branes as a result of the open strings that end on them, and in this talk I will discuss how these vector fields may impact the cosmology of the early universe. In particular, under certain circumstances they may play the role of vector curvatons and hence give rise to distinctive features in the curvature perturbation.