Of course this makes perfect sense. Amazon is bidding against its own affiliates, who are driving up prices and diluting its click-through rates (thus reducing click-through volume and further increasing its bid prices). In the cases where they are already the top search result, they don't need or want AdWords links from themselves or affiliates distracting the user and costing them money unnecessarily.
<i>Q: Was Amazon’s policy on bidding on words such as “amazon,” “endless,” or “kindle” changed?
A: No. Associates are still prohibited from purchasing or registering Amazon’s proprietary terms such as “amazon,” “endless,” and “kindle,” and misspellings of those words) to send traffic to any site. Please refer to the Operating Agreement for more information.</i><p>This sounds questionably legal. If I write a book about the Kindle, I can't buy a search ad to advertise it?<p>I really like Amazon, but not when I read things like this.