Most of current academic and commercial surface computing systems are capable of multitouch detection and hence allow simultaneous input from multiple users. Although there are so far only few applications in this area which rely on identifying the user, we believe that the association of touches to users will become an essential feature of surface computing as applications mature, new application areas emerge, and the enabling technology is readily available. As the capacitive technology used in present user identification enabled tabletops is limited with respect to the supported number of users and screen size, we outline a user identification enabled tabletop concept based on computer vision and biometric hand shape information, and introduce the prototype system we built to further investigate this concept. In a preliminary consideration, we derive concepts for identifying users by examining what new possibilities are enabled and by introducing different scopes of identification.