B. O’Donovan. (2005)introduces the notion of trust in collaborative filtering.
A simple memory based method is used to incorporate trust into a simple similarity based collaborative filtering algorithm. Results on MovieLens seem to be better than standard methods..
E. Wilde, S. Anand, and P. Zimmermann. Research and Advanced Technology for Digital Libraries, 9th European Conference, ECDL 2005, Vienna, Austria, September 18-23, 2005, Proceedings, volume 3652 of Lecture Notes in Computer Science, page 479--480. Springer, (2005)