In-app ad viewability is important because advertising can only be effective when it is seen by real people. As mobile ad spending continues to increase, higher measurement standards are vital for securing a healthy, thriving mobile ecosystem.
The current debate revolves around what should constitute an impression. Not all ad impressions are created equal — just because an ad server has delivered an ad to an app or mobile website does not necessarily mean that the user has indeed had a reasonable opportunity to see it. Therein lies the difference between an ad impression that is viewable and one that is only served.