Online video viewers' short attention span seems especially relevant to advertisers looking to strategically trim ad budgets as the economy contracts. For starters, it is clear that post-roll ads are of limited effectiveness. A three minute video that has a post-roll ad in the final seconds, for example, will only be viewed by 16.62% of the initial audience, on average.
Another takeaway is that overlay ads should be displayed as early as possible in a video, preferably within the first few seconds. On YouTube, where most overlay ads appear at about 10 seconds in, 10.39% of a video's initial viewers are not likely seeing the ad.