It's hardly a surprise that viewership drops the longer it takes for a video to buffer, but a professor has analyzed data from 6.7 million unique visitors to try and put some numbers with the trend. According to a paper published by professor Ramesh K. Sitarman of the University of Massachusetts, Amherst, viewers begin to abandon a video after a two second delay, with six percent disappearing per second thereafter. Depending on what kind of user you are, that may sound a bit low, but that may be due to the types of videos that Sitarman analyzed. The professor considered videos under 30 minutes long as "short" — we'd assume that your average minute-long YouTube video would lose far more users per second of buffering. As shown in the research findings, there's certainly some truth to that: roughly twice as many viewers gave up on "short" videos than long ones after a ten second startup delay.
The findings also sugest that our impatience with internet speeds looks to be an unwinnable battle. Viewers with higher-speed internet connections continually had a weaker tolerance for delays compared to those with DSL or mobile data connections. There may very well be a point when we'll no longer notice, but for now, it seems that you can never have enough speed.
Professor Sitarman's findings come from data collected by a content delivery company called Akamai, which is used by Adobe, Starz, USA Today, Verizon Wireless, and others. Sitarman helped build Akamai, and the company provided the space needed for the study, but the data comes from a very large sample and a spokesman told GigaOm that it didn't influence the findings.