TiredRobot.com does not use any google adwords campaigning.   If we review (in google analytics) the top traffic sources, I see “google / organic” as source #1 and “google.com / referral” as source #2.   What is a referral from google.com if there are no AdWords campaigns running (which should be tracked as cpc anyway)?    If they were unsponsored search result clicks, then wouldn’t they appear under the “google / organic” results?

I decided to post this answer since my initial search on Google was fruitless.   I had to go straight to analytics help (RTFM) and search:  “What is the difference between  ‘google / organic’ and ‘google.com / referral’?”

What does google[referral] mean?
Not all referrals from Google.com domains come through organic search or AdWords ad listings. Referrals may come from a variety of sources, including Google Groups posts, base.google.com listings, or static pages on related Google sites. Such visits are tagged as [referral] instead of [organic] or [cpc].