How do they know they passed? They solved everything, but got no offer? I haven't heard of such stories. Share if you know any.

This happened to me, I was going for the Customer Solutions Engineer role.

After the phone interview, they flew me to Mountain View. All day of one to one interviews; some face to face, some over Google Hangouts, did a coding-problem using Google Docs.

Got a phone call from the recruiter a week later saying I had passed all the interview however they had to go with a person who had a bit more experience in the particular customer industry they wanted to place the role. Judging by the questions and angle they were asking, I think it was Television (I come from the movie industry).

They still phone me from time to time again, asking if I'm interested in other roles (had an interview in London last year with their Android Team), so I guess time will tell if they find a position for me.

Interesting. I wonder if they will make you go over the interviews again if they find a position ;)

Yeah false positives are everywhere.