Do you have any links that go into detail on this? I was intrigued by your comment and I want to read more about it but ironically I couldn't find anything on Google!
I can't find the paper I read on it either, but I can confirm that it happens anecdotally with Google, and oddly enough AIM Messenger. I've had URLs that have never had an inbound link, and magically GoogleBot rocks up when I show a Chrome user. I'll keep looking for it.