“In Common” Field

Unless I’ve been totally oblivious to the existence of this data field, which is entirely possible, it seems that Google has made the people that we all have in common easier to find and see under the notifications tab. Wondering how someone found you? Have you been posting to Public and Extended Circles? Well, now you can start to figure out the ways in which people get to your information.How do you see who you have in common? Pretty simple — just head on over to that person’s profile page by clicking their name. The people who you have in common should be listed under their profile picture. On my profile, it’s above the “people in your circles” and the “people who’ve added you to circles” boxes.
You can use this back-tracking technique for several purposes — find people with similar interests, check out who is re-sharing your content consistently, and start to piece together the content which is bringing users to you.

Good luck. I’m off to play 6 Degrees of G+ Bacon.