The service will be optional for users and won't replace any of the traditional Google search options you're used to. What it will do is add another layer of results based on your social circle, which in turn could help deliver more relevant search results. For now, the functionality is still in experimental form, but users with Google accounts are able to sign up to use the service. Google also warns that early users may notice the button comes and goes as it makes improvements to the service.
Instead of appearing at the bottom of the page, social search results will be mixed into the regular search results, based on relevance. Additionally, notes below search results will show Facebook and Twitter contacts who have shared the link, along with their photo so you can see which stories and pages your friends are recommending.
Social search has always used contacts pulled from Google to determine your network, but now you're able to privately connect accounts you don't necessarily want made public, like your Twitter user name. If you choose to privately connect your accounts, they won't show up on your Google profile.
Today, Bing and Facebook announced a partnership, debuting Bing's new social search function. In short, it's a way to combine your friends' recommendations with other search suggestions, providing a complete set of results and information about any given topic. This new functionality will live both on Bing.com (in its own vertical) and within Facebook search.
Learn more about the new feature after the break.