Google's AdSense provides huge additional reach, but the conversion rate on contextual traffic is
often dramatically lower on the content networks than from pure search. Even with separate campaigns
and Google's smart pricing algorithms supposedly bringing things into line, taking effective
advantage of the content network is often challenging. Growing a campaign and extracting additional
profitable clicks from the keyword-targeted media ecosystem are never easy, but after your pure
search campaign has gone through several iterations of expansion and tuning, the only way (other than
fighting a bidding war and raising bids while ROI drops) is to expand the campaign by trying (or
retrying) content targeting.
Content is not search. So if you've tested and continue to use the same campaign structure for
content that works well in search, you may be missing huge opportunities.