A while ago I wrote an article for ITWorld entitled Chance encounters of the electronic kind. Serendipity, luck, chance, the road less travelled, gardens of forking paths, all play bigger roles in information discovery than we tend to like to admit.
I'm convinced that one of the reasons bookshops are still going strong is that they have an unparalleled ability to allow you to stumble upon stuff by accident. It is part of what makes libraries such wonderful places too of course.
The Flamenco search engine tries to bring some of that to the electronic world. Much needed IMHO.