Did you know that 85% of Facebook video is watched with no sound? Many people watch videos in places where they can't turn the sound up, or where there's background noise. Those are two important reasons why video captions matter. And, of course, video captions matter for accessibility. Include captions, and you will improve you click-through rate as those with hearing loss or impairment can still understand your video content. Captions also help with SEO by providing text that search engines can find.
According to a paper by Duncan Watts and colleagues entitled: "Everyone's an influencer", the most common risk in viral marketing is that of the influencer not passing on the message, which can lead to the failure of the viral marketing campaign. A second risk is that the influencer modifies the content of the message. A third risk is that influencers pass on the wrong message. This can result from a misunderstanding or as a deliberate move.