Philipp Schmidt, Christine Geith, Stian Håklev and Joel Thierstein have published an article on peer-to-peer assessment in the latest issue of IRRODL. From the abstract:

This paper makes the case for a peer-based method of assessment and recognition as a feasible option for accreditation purposes. The peer-based method would leverage online communities and tools, for example digital portfolios, digital trails, and aggregations of individual opinions and ratings into a reliable assessment of quality.