People in my life think I'm arrogant when I say I'm not interested in working for Google, but it's more just that it's not a "good fit" for either of us.
When I interviewed at the GOOG a year or two ago they asked me to rate myself on a 1-10 log scale for whichever skills I claimed to be proficient in. 9-10 was 'wrote the book' / 'invented the langauge' IIRC.
Given that Google employs or has employed Guido van Rosssum, Ken Thompson, Rob Pike, Brian Kernighan, and Josh Bloch, I think that would be a fair assessment of what "expert" means in the context of interviewing there.
It might be apocryphal, but at one point candidates filled a "rate yourself from 1 to 10 in technology X, Y, Z" to help guide the interviewers in choosing questions. The general consensus was "if you rate yourself as a 10 in Python, there's a non-zero chance you'll end up with Guido on your interview panel"
Funny. One of the Google recruiters told me that expert at technology X meant you either wrote a book on or invented X.