martinibuster - 6:22 pm on May 25, 2010 (gmt 0)
An open market PPC system may result in ads that may not be in the best interest of site visitors. I'm thinking of ads that lead to squeeze pages that promote dubious schemes and e-books of questionable authority or usefulness.
Allowing the targeting of specific forums may result in ads that members may find objectionable. For example, members frequenting the content forum may find ads for content generation software objectionable.