Clever cross-promotion from Amazon and A9.com

I just completed an order on Amazon, to purchase incredibly important books such as Go, Maisy, Go!, my son literally squeals with delight whenever we read Where Is Maisy?, he loves pulling the flaps open and gets visibly excited when he sees the last page of the book.

I was greeted with the following text:

KC Lemson, since you've been using A9.com recently, virtually everything at Amazon.com is automatically an additional π/2% (1.57%) off for you. Collecting this discount is zero effort on your part. It will be applied automatically at checkout (it will happen whether you use the shopping cart or our 1-Click Shopping®). You don't need to do anything to get this discount except keep using A9.com as your regular search engine.

We don't advertise this additional discount that we give in exchange for using A9.com, so if you want your friends to know about it, please tell them. It is probably the only way they'll find out. All they have to do is use A9.com as their regular search engine. They should make sure they are signed in to A9.com (it should be recognizing them by name) so that we can be certain they get credit for their visit.

My thoughts on this promotion:

#1: It's an interesting idea to do cross-promotions like this. I'd like to see it on sites that are more closely tied to each other than a search engine and Amazon, though - for example, if Amazon noticed that I was using drugstore.com (which is a partner of theirs), then Amazon could slip me a little sumpin' as a thanks.

#2: It's cool that the discount is pi over 2%. Geek chic. It's like the google job ads.

#3: It is kind of creepy that the cookie A9 left on my machine was picked up by Amazon. But at the end of the day, I prefer cookies to none. I run adaware every once in a while to clean up the tracking cookies but I don't lose sleep over it.