Intelligent objects and devices are becoming part of the environment where people live. The more mobile and pervasive computing becomes, the greater opportunity users potentially have to customize the computing activities that take place around them. For some people the availability of devices and services offers possibilities for tailoring things to exactly what they want. For others, however, this represents a problem: how to manage the complexity? It is neither practical nor economical to use professional software developers for individual tailoring. Thus, we have to provide users with easily operable tools for service composition. The goal of this paper is to highlight the main challenges for a meaningful end-user tool support.