Stefan, thanks for the video.
Google has been offering personalized searches when logged into your account for sometime now. They introduced the "Social Search" in 2009 but just recently started to integrate their "Social Search" into the mix when you are of course logged into our Google account.
You bring up a great question on the "You Shared" - Here is Googles answer...
"We’ve made Social Search more comprehensive by adding notes for links people have shared on Twitter and other sites. In the past, we’d show you results people created and linked through their Google profiles. Now, if someone you’re connected to has publicly shared a link, we may show that link in your results with a clear annotation (which is visible only to you, and only when you’re signed in)."
Google has also added the option of connecting your accounts.
Here is a video from Google that explains more of this...