The actin cytoskeleton is a fundamental system in cells powering a diverse array of functions including adhesion, division, and motility. To perform these functions, cells must be able to control the architecture and mechanical properties of this system in both time and space. This control is achieved using a wide range of actin binding proteins that regulate these properties by controlling nucleation, severing, and crosslinking. In this talk, I will discuss our past and ongoing work using theory, modeling, and molecular simulation to describe how the regulation of these properties can be performed in a passive way, i.e. with only simple physical principles and competition between binding proteins. I will then discuss how actin binding protein affinity and activity can be altered by non-equilibrium processes such as myosin motor activity and actin filament polymerization. The interplay between these passive and active processes presents new mechanisms that must be considered when designing new experiments to probe regulation of cytoskeletal structure and dynamics.