Graham wrote "Does anyone have any experience preventing/defending against potential defamation issues arising from online reviews?" i think the secret here is certainly in preventing, or at least removing personal (ie your) responsibility by incorporating a Terms and Conditions of Use statement that poster need to accept BEFORE being able to post reviews to your site. You are merely providing the mechanism for the reviews. (Not sure where or whether you would be able to get a generic statement from, off the top of my head though. Perhaps someone else might have an idea). In conjunction with your review process, your back should be covered. does this help or am i completely wide of the mark? any other comments?