From the Google Inside AdWords blog:

Based on advertiser feedback, and our commitment to provide useful tools and information for our advertisers, we’ve now added search volume data to the Keyword Tool.

…

These approximate numbers are intended to provide better insight into keywords’ monthly and average search volumes than previously provided by the tool.

If you’re new to Google AdWords, their Keyword Tool previously provided a visual cue which indicated search volume.

If you want to check it out and your not currently an AdWords user you can use Google’s AdWords external keyword tool.

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The new ads are for Google AdSense for content sites. AdSense publishers can decide if they want to participate in the program or not. Participants will be able to review details of the advertisements which will appear on their site and decide if the ads are appropriate for their site or not.

One would assume that the amount paid for an actual conversion will be far higher than what one gets for a click under the current PPC model-especially as the amount will be able to be determined by the Advertiser, setting up a affiliate-like relationship, brokered by Google.

The program introduces new challenges for those managing a web site with the ads. With PPC, the user had little control over what went on their site and only had to rely on ad copy driving a click. Now, they’ll have to consider if the web site the user will visit as a result of a click has the potential of closing the deal.

Update: Google’s Inside AdWords blog has a post specifically about the Pay-Per-Action beta.

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