What does it mean for online content to “go viral”? An analysis of almost a billion information cascades on Twitter news, videos, and photos has produced the first quantitative notion of whether something has indeed gone viral, thereby enabling further research into topic experts, trending topics, and viral-incident metrics.

See the original post at http://research.microsoft.com/apps/video/dl.aspx?id=185452&l=I with links to several video formats.