We cannot control what recipients do with the information in a disclosed credential. As a result, policies might demand credentials from the requesting party certifying that it will not, for example, resell the information gathered during trust negotiation. Complicating matters, the parties can sometimes infer credential information from the policy disclosures made during negotiation. Privacy guarantees for parties negotiating trust are an interesting area for future research.
K. E. Seamons, M. Winslett, T. Yu, L. Yu, and R. Jarvis. Protecting Privacy during On-line Trust Negotiation. 2nd Workshop on Privacy Enhancing Technologies, San Francisco, CA, April 2002.