Late Thursday, Google announced the largest changes to their US AdWords policy in some time. Previously, trademark owners could prevent anyone from using their trademarks in their ad copy. Now, resellers and information sites may utilize the trademarked terms in their ad copy.
This shift will likely be a boon for shopping comparison sites, review sites, and likely the websites of many affiliates. It will also likely increase the number of ads found on trademarked searches and make policing trademarks that much harder.