The title of this post may be a bit extreme but the point is that with any segmentation, whether self selected or not, does tend to steer us toward things we are more inclined to like vs. those that we don't. See Apple, Fox News, or any other brand people have affinity to. Such is the tenet of a recent Slate article by Jacob Weisberg. I'm a long time fan of both Slate and Weisberg and thought this article was a great read on the tendency for media (any form really) to focus our attention on their agenda (and presumably yours) at the expense of a broad array of information sources.
Weisberg does an experiment of asking 5 different friends and family with different political bents what Google results were returned for 4 different politicians. The results were more similar than different, surprising the author to some degree. However, he didn't mention whether these 5 individuals were avid consumers of online political media which is what Google would have based its results. Got to have the garbage in to get the garbage out, right? In any case, I liked the premise and believe his central tenet is spot on when it comes to media consumption.
For e-commerce, its another matter. Anyone who has had an Amazon account for a number of years and shopped for gifts for others or simply racked up a double digit purchase list can attest that Amazon doesn't forget easily. They will suggest baby products till the end of time if you bought that shower gift for your brother 4 years ago. (Hey, Amazon: how about evolving the recommendations over time so that you now suggest toddler products for that 4 year old rather than stick to baby gift ideas?