Altmetrics (alternative metrics) is a recent development whereby social media sites such as Twitter and Facebook, reference managers such Mendeley and Zotero, and blogs and news outlets, are watched in order to track and share evidence of the online impact of a paper.  Scopus has now added an Altmetric feature to the database, located as a sidebar (scroll down), for those references for which this data has been collected. Here is an example of such a reference. To read details of this new Scopus initiative, look at Altmetric for Scopus.