Sudden drop in / referral traffic while / organic traffic stays steady

[Shatner]

This week I've seen a sudden, massive plummet in my traffic coming from google.com/referral. We're down about 60% in just the past few days. What makes this REALLY weird is that there has been no change at all in our google.com/organic traffic.

Aren't the two linked? I thought /referral traffic was things like Google search results being displayed on AOL and so on.

Or am I misunderstanding what google.com/referral traffic is?

[Mentat]

Maybe Penguin 2.1 has affected a lot of your referers...
I also see this.

[Shatner]

I am right though in thinking that referrers means sites outside of Google using Google's search data, right?

Like Aol.com search is just Google search results. That's a referrer?

Defining exactly what a google.com/referrer is has always been kinda vague.

[lucy24]

What's your source of information? Anything other than raw logs is subject to interpretation. In particular, analytics programs other than GA may or may not recognize that a bare "www.google.com" (without query) is a search result, not a direct link.

[Shatner]

Google Analytics, obviously. Anyone using raw logs probably doesn't have a very big site.

Sooo I ask again... What is Google.com/referral traffic?

[Mentat]

Traffic that come from links on other sites!

[Masaai]

"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]."
--source: Google Analytics