More and more companies detect the power of crowdsourcing as a new form of user interaction and a source of collaborative innovation. Besides the benefits of gaining many innovative solutions to a posed problem, idea and design contests are supposed to have a favorable impact on participants’ loyalty intentions towards the hosting firm. The basic argument is that the ongoing involvement over several weeks with a company and its products, and the personal engagement that occurs while developing new ideas for this company, would lead to an increase in loyalty. With our research we challenge this assumption; we argue that the mere participation in idea and design competitions will not enhance loyalty, but that perceptions of how fairly a company treats the idea competition community will explain changes in loyalty intentions. We analyzed a LED-light design contest launched by OSRAM, a leading lighting manufacturer. We investigated the impact of three fairness dimensions (distributive, procedural, interactional) on participants’ future behavioral and attitudinal intentions. The results suggest that the impact of fairness perceptions is dominant, i.e. no amount of joyful experience during the co-creation event can compensate for low fairness perceptions. Furthermore our analysis reveals that the influence of the fairness dimensions is asymmetric: while distributive and procedural fairness can be considered as basic factors that must be fulfilled in order to avoid negative behavioral consequences, interactional fairness is an excitement factor which causes truly positive behavioral consequences.