BizSugar.com › Social Media › Google Launches +1 (Plus One) Recommendation Button

To display the correct +1s to you, Google uses several signals to identify the best useful recommendation. These include the people that are already connected to you through Google like your chat mates and contacts. Before long, Google will also include other signals like your relation to sites like Twitter and Facebook so that Google can make sure that your recommendations are as relevant as possible to the search query.