In the United States, Nielsen has long been the main source of data for evaluating television shows and stations for advertisers. It's considered a very reliable source. So their inclusion of data on web video watching habits in their 2011 report on the "The U.S. Media Universe" is a real boon to anyone planning to enter this field. It's interesting to ask what are the consequences to free culture productions and the free software used for creation and consumption of video arts.
There's a lot of information in this document, and a lot of infographics that make it quite easy to digest.
Some interesting points:
From my own experience, I interpret at least part of the reason for this to be the difference in comfort level -- while I will sit through a 5 or 10 minute video, I'm not comfortable sitting back and watching a movie on my computer. I expect to be actively involved when I'm in front of the computer.
But this could all change. Better (and freer) home video entertainment systems with integrated computers might make internet video more acceptable for longer works. Greater availability of longer web series in easy-to-download forms might also attract more viewers.
It seems likely that sites which attempt to impede people from downloading video so they can transfer it to a more comfortable "home theater" environment may be limiting people to shorter videos they are willing to watch on their computers or smart phones. Free culture productions that allow easy downloading of ISOs or high-definition video files might therefore have a significant advantage over proprietary competitors.
The document is also available as a PDF.