Most multi-user horizontal interactive surfaces, or tabletop computers, cannot determine which user has performed a given action. These tabletops are less capable than identity-aware (IA) tabletops, which can. However, current research on IA is scarce and speculative. Notably, no one has rigorously compared the power of IA and non-IA devices, so evidence that IA enables groups to work better together is lacking. My thesis establishes an identity-aware perspective for interactive surface design. First, I have constructed an experiment to determine that IA can improve the effectiveness of small collaborative groups. A second experiment compares several emulation techniques designed to bring the benefits of IA to non-IA devices. I explore IA in detail through examples, present some open problems involving IA, and discuss promising solutions. Taken as a whole, this document serves as a comprehensive introduction to the study of identity awareness and a springboard for future research on the topic.