One of the article that you may be interested  in reading about is 'From bibliometrics to altmetrics :
A changing scholarly landscape

Excerpts;

When future Science Citation Index founder Eugene Garfield first came up with the idea of journal impact factor in 1955, it never occurred to him “that it would one day become the subject of widespread controversy.”

Today, techniques for measuring scholarly impact—traditionally known as bibliometrics —are well known for generating conflict and concern, particularly as tenure-track scholars reach beyond previously set boundaries of discipline, media, audience, and format. From the development of more nuanced academic specialties to the influence of blogs and social media, questions about the scope of scholarly impact abound, even as the pressure to measure such impact continues unabated or increases. 

Read complete article at: http://crln.acrl.org/content/73/10/596.full