Google getting hypersocial

While doing Google search, I just noticed this new suggestion today, Google knows about my Twitter id and wants to suggest me what my friends are talking about. See the box which says "Want to see which results your friends ..." I don't think I have told Google about my Twitter id, but they somehow know it. Looks pretty cool though.

When I click on the button they add my Twitter id to my profile.





I don't see any changes in results.

Was it that Google was testing some new feature?