In inter-enterprise collaborations, autonomous services from different organizations must independently determine which other services they can rely on. Reputation-based trust management in Pilarcos utilizes shared experience information on the actors’ past behaviour in estimating the risks of a collaboration; these experiences are shared between members of the service ecosystem through a reputation system. As the reputation system becomes an essential peer-control mechanism for the open service ecosystem, it must be augmented with sanctions for misbehaviour and appropriate incentives for correct behaviour. A fair sanctioning system cannot be built on traditional subjective reports, as rebuttal of undeserved reports requires shared, objective measures. To make the shared experience information objective and verifiable, we associate it with whether the relevant collaboration contract was followed, backed up with evidence in the form of nonrepudiable receipts. In this way, we are able to protect automated reputation-based trust decisions from being skewed by misinformation.