Now it's possible on Youtube to link directly to a specific timepoint in a video. So you can refer to a particular section of a video.
Argument: I guess this is a need for people to link to specific timepoints, like linking to anchors in HTML-Files, especially for longer videos (I already had the need). I was inspired to this idea by the TED-Videos, which are seperated in different chapters.
Current development: Viddler (comments for specific timepoints in videos)