Bing's announced some big changes to their paid search advertising policy that will allow the use of trademarks in ad text and as keywords for triggering ads, closely mirroring Google's update last year. These new changes go into effect tomorrow (3/3/11), and apply only to ads targeting the US or Canada.
Along with relaxing trademark restrictions, Bing will cease mediating trademark complaints, stating in their updated policy: "Please note that Microsoft is not a mediator. As such, Microsoft encourages trademark owners to engage directly with advertisers who they believe are misusing their trademarks." If advertisers are uncooperative, Bing provides an IP Complaint Form trademark owners can use to take down individual ads.