Altmetrics uses the social web: tweets. Facebook-likes, social bookmarks and other social media to follow the discussions surrounding a research article and other scientific material. Altmetrics studies a specific article’s impact; article-leverl-metrics in other words. The term altmetrics was coined in 2010 and Martin Fenner, editor of the special issues, writes that altmetrics have grown up. Focus has moved from whether it is possible to reliably collect altmetrics (this can of course still be debated) and what is the value of this date and can it be used together with statistics and citation as a complement to presenting best practices and how altmetrics could help us to understand how research impacts the society. There are many areas to study, e.g. to counteract missuse and gaming altmetrics.
Altmetrics is an interesting area and these metrics consider the specific article and discussions which have followed but these number can also be gamed which could make them unusefull. You can game these number same you can buy journal impact factor, number of citations etc. Danger is that the same organisation and people which are tarnishing open access publishing will (if they are not alreadly) abuse this. Read Scholarly Kitchen’s blog post on how easy it is to game Google Scholar citations.