The "serendipitous encounter"

It applies not only to people but to books, maybe even on-line. Here is an interesting insight:

Google has something all of these platforms don't have: a specialism in "discoverability". If Google can somehow leverage its skill in this area, then there is a possibility that it could open up a world of published content online in a way that even Amazon has been unable to so far. Google could begin to replicate the bookstore experience, particularly the serendipitous nature of many purchases -- or to put it another way: books found when searching for something else.

via thebookseller.msgfocus.com

"books found when searching for something else."

That's how the best friendships are found.