Starting in November 2011, Google+ profiles are used as the background account for many Google Services including YouTube, Gmail, Google Maps, Android, Google Play, Google Music, Google Voice, Google Wallet, Google Local and more. As of January 10, Google Search is customized with a feature called Search Plus Your World, which inserts content shared on Google+ profiles and brand pages under Web Search results, if one is logged into their Google+ account while using it. The feature, which is opt-in, was received with controversy over the emphasis of Google+ profiles over other social networking services. The feature builds upon the earlier "Social Search" feature which indexes content shared or published by authors; "Social Search", however, relied partly upon returns from non-Google services, such as Twitter and Flickr. Google and Twitter had a contract that expired in July 2011 which is the reason Tweets are no longer shown.