The argument is that online sharing does not invoke the same behaviours as traditional methods and consequently needs it's own set of metrics. There are different characteristics to the behaviours and these generate different data that that traditionally collated by impact factor generators, therefore creating the need for a new appriach to measuring impact > Altmetrics..
For example Elsevier clusters like kinds of activity for this type of reporting, rather then compressing all activities into one.
Definition
"Altmetrics are new metrics proposed as an alternative to the widely used journal impact factor and personal citation indices like the h-index. The term altmetrics was proposed in 2010,[1][2] as a generalization of article level metrics,[3] and has its roots in the twitter #altmetrics hashtag. Although altmetrics are often thought of as metrics about articles, they can be applied to people, journals, books, data sets, presentations, videos, source code repositories, web pages, etc.[4] Altmetrics cover not just citation counts, but also other aspects of the impact of a work, such as how many data and knowledge bases refer to it, article views, downloads, or mentions in social media and news media."
From & See more at; http://en.wikipedia.org/wiki/Altmetrics
Image from : http://altmetrics.org/wp-content/uploads/2010/10/four-ways-to-measure-impact-copy.png
Leaders in the field include
AltmetricsPlum
PLOS (code)
Impact story .org (free (plugs into Google Scholar My Citations)
Some of these interact with other services such as Vivo, Profiles, SciVal, Experts, and Figshare.
Altmetrics are starting to appear in subscription resources as sub products or reports.
Altmetrics are a way for crowd sourced / funded projects to measure their success in reaching their targets. They enable researchers to be able to assess whether they are reaching the right market / population with outreach and gives context to the research / paper.
Recent trend
Tweetable abstract submissionsSpaces to watch
growkudos.comORCID
Counter (use in Institutional Repositories).
Read more at : http://altmetrics.org/manifesto/