On e2, travelling from any node to another requires a link of some kind. This is basically assumed knowledge but stated here for clarity. By following a series of links, you are travelling a node path.
Simply put, a node path is a series of links travelled to move from one node to another.
Desire and The Tardis Effect
e2 can look deceptively small at times, this is what I like to call the tardis effect, named after Doctor Who's ship, the Tardis, this looked like a small telephone booth when in actuality it was a huge spaceship. While there are a substantial number of nodes in existance, any one person will only be interested in or desire to see a certain number of topics.
Soft links provide a series of (usually) related topics, as nodes, these deviate from the original but typically hold the same focus. By having a certain amount of choice as to where within these topics you move, you will usually find yourself centered around the same topics of interest.
Through people's desire to read information about things that they are interested in, they will usually find themselves looking at the same or similar information.
Reversing The Link
Given that node paths tend to be dictated by what the person in question is interested in, this can then be simply reversed. Think of a node you looked at and try to remember the node path between it and the one you started from. Individual nodes would be harder to remember, but if you stick to simply thinking of what topics of interest the nodes you visited would fall in, you can begin to use it to analyse things that pique your interest.
Widening The Scope
This phenomenon is not exclusive to e2, by any means. Any hyperlinked data system will show similar patterns. Of course, an obvious one would be the internet. Billions of information resources, all linked to each other. By objectively monitoring the way you browse, you can find similar patterns. Indeed, the internet has its own tardis effect
So What's The Point?
Any selective information resource will experience its own form of the tardis effect. More importantly, any selective information resource will reflect the person selecting it and by monitoring the way you select your own information you can find a lot about your interests and the things you like to learn.