Here is an updated movie (with sound) describing how Reflections, Environment maps, HDRI or HDR textures and Background objects interact with each other to create realistic looking glass and reflections. Background object are nice for video because you can preview the video in the Editor. Unfortunately, they don’t show up in Reflections or Refractions on transparent objects. That’s why I typically use a Plane with a video applied to it.

Alternatively, skip the Reflections all together and go with an Environment Map which will render much faster. You can specify the video to be an Environment Map so the motions still shows up and a lot of times this looks more realistic anyway.

Related modules:

Environment vs Reflection
Compositing Video with Reflections, Environment Maps
Video importing
Video attached to part of an object
After Effect Project File