Over the past few years, traditional software products, sales and licensing schemes have declined, whereas business value and revenues have shifted to SaaS-based schemes. Even so, most research has focused primarily on the technical layer (i.e. service invocation, integration, coordination, etc.). As a result, most SOA solutions available on market still do not feature a service "face" for human users. The SOA front-end of those that do is typically based on monolithic, rigid and non-customizable user interfaces and portals that invoke back-end services and processes ad-hoc. This paper presents the rationale behind a novel user-centered visual service composition system being developed by the European FP7 FAST Project consortium. This service composition system aims to enable service composition by guiding non-technical users through an open innovation process. The proposal formally models the component model, techniques and languages. Also it leverages some well-known Web 2.0 principles in order to bridge the gap between the service technical layer of a SOA and its end users. This should improve user appreciation of the benefits of such a system, enabling them to easily mash up their own service front-end from its basic and/or available building blocks.