Information Determinism. Scary stuff! Sadly, it sounds pretty reasonable. Think about it this way- we become like characters in a console RPG like Fable where every choice we make is locking us into a path because the Algorithms that are looking for key data indicators are channeling us this way and that.
Every time we make a choice, or a search, we’re slowly building a giant pile of data that will be used in certain ways to determine what we’ll be shown and where we’ll be sent online. Facebook is using these systems to even determine who our friends are, since our News Feed is being modified to just show us the people it thinks we most want to interact with based on our interactions with people. This will only get worse and worse with time, as the internet we see will become more and more customized to us and our tastes in an effort to keep us using it as much as possible. (To sell us stuff and make money from us.)
Not sure how to counter this, except maybe not using Facebook or other social networks, using Duck Duck Go for searching, and maybe proxies. But, if you want to use the Net at all for shopping, you have to log in somewhere, Ebay, Amazon, it doesn’t matter. And you will leave a trail, and they will use that data to try to sell you stuff, here, or in the future, it will happen unless you’re an ultra secretive and ultra-passive user.
A better route might be to give them too much confusing and conflicting data so they don’t know what boxes to stick you in. Or, since you know they’re watching, give them data which manipulates them to give you what you want. After all, if you show interest in a book with your Amazon account logged in, and then wait a week or two, you’ll get an email offering you the book at a greater discount. With a little knowledge and patience, you can use the system more than its using you.