If you are an advertiser running Google AdWords on the content network, the only way to know where those ads are being run is to dig through raw logs and extract the content site URLs from the massively long AdWords referral strings. But in an article in the New York Times about competitor Quigo, Kim Malone from Google has revealed that they will be listing all URLs where advertiser's ads are appearing.
In the next few months, Google’s advertiser reports will begin listing the sites where each ad runs, Ms. Malone said.
I think this transparency is a good thing and could encourage more advertisers to opt-in to the content network if they are able to easily determine (and thus block if needed) the websites their ads are being displayed on. For more details and analysis, please see JenSense.