I was looking at Macenstein earlier. And was slightly surprised after a while to notice that amongst the Amazon ads appearing on the right were some for very familiar stuff.
Turns out that Macenstein is feeding me my own personalized Amazon data. And it looks as if other people might be similarly surprised as there are several links to 'privacy information'.
This explains that Macenstein is an Amazon Associate Web site.
Although we may use your Amazon.com cookie to determine whether you are a recognized Amazon visitor and to offer personalized content (such as product recommendations) and special offers, we do not keep or attempt to construct a record of the Web sites you visit. [Amazon.com Associates Privacy Information]
And in response to a question about whether these 'placements' are the same as the personalized recommendations you would see on Amazon itself:
They can be. The products you see listed when visiting an Amazon Associate's site can be based on a variety of factors, such as that site's topics and sales history. We might also show you items based on your own personal purchase history at Amazon.com. The Associate Web site hosting this Amazon.com link does not have access to these "personalized" recommendations. [Amazon.com Associates Privacy Information]
I thought this was interesting for several reasons. It is another example of how what we see is increasingly situational, dependent on what a service knows about us. I saw this from our home machine. I would see something different from my work machine. It is also an example of what Steve Rubel says in a very interesting post about making content embeddable in fine-grained ways: "traffic is becoming something that happens elsewhere".
In the very near future portals including iGoogle, My Yahoo and Netvibes as well as social networks will be able to easily inhale the smallest pieces of content from across the web. Don't wait. Start now to make everything on your website embeddable. Traffic is becoming something that happens elsewhere, not just on your site. [Micro Persuasion]
The Rubel reference, well worth a read, is via dlf-dispatches. Twittering Stu also discusses it.