In an information economy, you have to turn an invisible conversation into a metric. Once you have a metric, you've grown a long tail.
Google’s New Metric For YouTube Ads: Brain Waves: "YouTube has recently been pushing overlay ads which appear in the lower portion of the window while the video is playing. Since these ads are often used for branding purpose looking at click thru measurements would not give a true picture of their impact upon the advertisers brand messaging.
To prove the efficacy of these ads, Google hired a company called NeuroFocus to conduct research measuring biometric response to the overlays through indicators such as brainwave activity, skin response, and eye tracking. The study discovered that viewers found the overlays “compelling and engaging” and that these ads generated a high amount of attention and emotional engagement for a variety of different brands and video types. In addition, including a companion banner alongside the overlay ad was found to improve brand response compared to banner ads alone."