The common definition of a Reaction Video is one where the subject is reacting emotionally to some other video they are watching. It is a common tactic some video producers will use to hijack the existing interest in a popular topic in order to get views for their own video.
15 consumer examples of effective video marketing and 4 B2B examples of effective video marketing.
Cool Video Insights Tool: The YouTube Trends Dashboard provides insight into currently trending videos and the audiences that like them.
David Erickson discusses some of the factors that contribute to what makes a video go viral.