Trust and reputation systems gained great attention in the last decades. Such systems aim at giving users a quantitative evaluation about the trustworthiness of other users. Several metrics achieve it by combining the past direct experience of all the users of the trust network. Among the methods developed to assess trust, EigenTrust is one of the most popular, based on an adaption of the PageRank metric to trust systems. In this paper, we investigate EigenTrust dynamics, trying to explain some hidden behavioural patterns. Our aim is to show that EigenTrust metric exhibits some counterintuitive behaviours when compared to the common sense notion of trust.