Found this little article that states you will lose at least 20% of your audience within the first 10 seconds of playback. One for the editors I think.
http://corp.visiblemeasures.com/new...nchmarking-Viewer-Abandonment-in-Online-Video
http://corp.visiblemeasures.com/new...nchmarking-Viewer-Abandonment-in-Online-Video