The incorporation of a trust network among the users of a recommender system (RS) proves beneficial to the quality and amount of recommendations. Involving also distrust can offer additional clues how to handle specific recommendations as well as protection against recommendation attacks, yet this direction has not been thoroughly explored so far. In this paper, we advocate the use of a trust model for RSs in which trust scores are (trust,distrust)-couples, drawn from a bilattice. We design an experimental setup to get insight into the trust propagation problem in a movie RS and propose two trust score propagation operators, each reflecting a distinct user behaviour pattern or profile.