The title of this post probably mislead you, but identifying friends is just a subset of what Google is trying to do here.
If I'm searching for a good online backup service I care more about the opinions of people I follow on twitter than those of my non-technical friends and family, etc.
Good point I hadn't considered the real purpose of the service. But one thing I can't understand is why google - the kings of simple - want to include such messy data? When I see "do more" I smell failure.
Google doesn't mind messy data at all. Their goal is to get more data, even if it's not perfect. If they can get massive amounts of data, their statistical accuracy will improve.
If I'm searching for a good online backup service I care more about the opinions of people I follow on twitter than those of my non-technical friends and family, etc.