jimbeetle - 10:01 pm on Sep 4, 2007 (gmt 0)
Google knows [google.com]:
Content clicks may be priced differently than search clicks. Using smart pricing, AdWords automatically adjusts the cost of clicks for keyword-targeted ads that appear on content network pages. While you set one CPC bid, if our data shows that a click from a content page is less likely to turn into actionable business results — such as online sales, registrations, phone calls, or newsletter signups — we reduce the price you pay for that click.