Blender 2.74: When "Use Backdrop" is checked in the VSE, we can see the video clips in the background of the VSE; the clips will adjust to the size of the VSE, they'll be "full frame". I'm trying to have the display of video clips smaller within the VSE. On this video: https://www.youtube.com/watch?v=QnM_UAsLHag&t=3m53s at 3'53, using Blender 2.73, with the shortcut V (background image zoom), he can reduce the size of the clip and move it anywhere he wishes. I haven't manage to select the background image and reduce it's size. Has this feature been removed in 2.74?
Gooseberry request: Backdrop for sequencer.
There has been another request rB9a934 for an "Overdrop" what is exactly what you saw in your Video which has zoom functionality and can be dragged around. But it differs from the Backdrop feature you asked for. Actualy it's an evolvement of it and got renamed.
But as it is in development with feature branches not everything that is being developed for an Open Movie project finally gets into the Master Branch of Blender. Not every feature is bug free or already polished enough and therefore this would take too much time to merge it back into master.
A detailled description what has been merged back from Gooseberry is in the Blog article Gooseberry in Blender Master and unfortunately for the Sequencer only
A backdrop feature
has been mentioned there. Not the "Overdrop" feature. So your missing feature has not been removed, it just never made it into the "official" Blender development branch that results into the Version you can download from blender.org/download. You might ask the developers to merge this Overdrop feature back into Master as well.