Sean Liu then officially published it on Google+ saying:
Starting today, we’re rolling out a new experiment to show a Share link in Google search in place of the +1 button, making it easier for you to share a great website with your friends. Now when you click the Share link next to a result, you can add a comment about why you found it useful. You can then choose if you want to share it publicly or just to your Circles and it will post to your Google+ stream, making it easier for you to share directly from the search results page. This will appear for those searching in English.
Before, Google had +1 buttons in the search outcomes and then after that, they attempted thank them buttons in the search results.
I think how long this one will last?