Digital marketing services company Experian Marketing Services's latest report shows the picture sharing website Pinterest has become the 3rd largest social network website in US following Facebook and Twitter. Its visits are more than LinkedIn and Google + now.Experian conducted a survey about social networking site visits in March,2012, the results show that visits of Facebook were more than 7 billion  Twitter got 182 million visits, Pinterest 104 million. However, the survey does not include mobile traffic.Pinterest's visits in March were more than LinkedIn, Google + MySpace, a...