Google+ is fairly unusual and it just got a bit more unusual today. If you search Google, you might see Google suggesting that you thank your friends for +1ing the search result in Google+.
For example, I searched for [google] on Google and Google said I should the following people for +1ing the page on Google+. Here, Robert Scoble and Danny Sullivan +1ed Google.com and Google suggested I should thank them.
Then the Google+ share box will come on, specifically sending a message to Danny and Robert (limited share) thanking them for +1ing it on Google+.
This is what the share looks like in my Google+ Stream:
Update: Google sent us the following statement:
Just like you would thank a friend in person for giving you a helpful recommendation, now if a friend's +1 helped you find what you were looking for while searching on Google, you can immediately thank him or her by clicking the "Thanks" link right in your search results and writing a quick message. When your friend signs in to Google+, your thanks will appear in his or her stream. We're continuing to try out new ways you can interact with the people you care about right on the results page.