Sarah Perez writes:

Shareaholic is defining Google referral traffic as those referrals that don’t come through organic search or AdWords, but on other Google properties, like Google Groups or static pages on related Google sites. It does not, however, include Google+.

StumbleUpon reached 25 million registered users in April, and was seeing around 1.2 billion Stumbles per month at that time. Meanwhile, Pinterest doesn’t talk user numbers but is currently estimated to have around 20 million users, based on third-party sources.

So Pinterest users click out of Pinterest a lot.

Good for growth hackers looking for distribution, since Pinterest is now the #4 traffic referrer after Google Search engine, Facebook, and Yahoo:

something must be right.

Yes. 20 million pinners can't be wrong.

That Bing traffic referral was previously number 1 surprised me. Fascinating insights, thanks for sharing.

Bing was number 1 among that group, but still well behind Google organic, Direct, Facebook, and Yahoo.