As video is most popular on social networks it may not astonish you, that social means are important to video discovery. But the results of a survey conducted by Yahoo found the high ratio of 8 out of 10 videos are viewed because of some kind of social interaction. This concerns the audience of regular video viewers in the age between 16 and 44.
In particular the discovery by social means is devided in 50% of videos being found on social networks and 45% of some kind of recommendations by word of mouth. The second most important behavior to find videos is browsing, which is done by 7 out of 10 regular online video viewers with 45% finding stuff by active browsing and 34% watching stuff recommended while browsing.
Further forms of accessing video content is active search and using video aggregators. Ads are of minor importance, but still happens 20% to find content. Interestingly video aggregators are the most important means to access video content actively.
To get further information access the summary within the article Social Networks Play A Leading Role in Online Video Discovery or access the complete results published by Yahoo Advertising: Why Online Video is a Daily Habit.