I recently had a long conversation with Google (including the content PM) about the content network.

Here are a few suggestions from Google about the content network (most of these should not surprise anyone):

• Only the first 50 words in an AdGroup are used to determine its theme
• When an AdGroup has a large keyword list, Google’s matching isn’t as good and can get confused
• If an AdGroup is only shown on content, then it can be very useful to use more general words
• All keywords are treated as broadmatch when matching the AdGroup’s theme for content matching
• The Google recommended content bid is usually 75% of the search bid
• The typical content CPA (which I’m not sure if I can share so no numbers) is not significantly different (less than 10%) from search and content
• Of course, this is significantly impacted by bidding content and search differently
• It can be very useful to use site targeting with CPC bidding for ensuring your ads are shown on the highest converting content match websites

Content match resources:

• Search Ads & Contextual Ads Are Different! You Need To Treat Them Separately
• How to optimize a contextual search advertising campaign
• Block low quality traffic
• Peak behind the curtain to see to learn what AdSense sites are doing for you
• About smart pricing

On a side note, I finally responded to the comments about quality score and exact match impressions.

• AdWords shows more content network visibility
• Combat Click Fraud By Blocking Low Quality Traffic
• AdWords Makes it Easier to Control New Campaigns
• Google Local Business Ads Coming to G Map Mashups
• Local Business Ads to be syndicated to Maps API Sites