First off, it's pretty incredible that a 2D movie could be converted to a 3D movie. Usually a 3D movie has different perspectives, so I'm not quite sure how this technology works. But, YouTube seems to have a pretty good understanding because they are now allowing any 2D clip to be converted to 3D. It's not just for video creators anymore!
Any ordinary user will be able to watch certain 1080p videos and convert them to 3D. The option will be in the Quality settings pane. Upon clicking it, Google sets to work converting the video into 3D. YouTube analyzes a host of video components, including "color, spatial layout, and motion to estimate a depth map for each frame of a monoscopic video sequence" to create the 3D effect.
However, usually if the video wasn't shot in 3D, the effects are somewhat boring. And 3D just gets old after a while if the effects aren't up to snuff. Google disagrees, saying that hundreds of thousands of videos were converted in the past months by their respective content creators. Also, how many people are set up to watch 3D? I know I'm not.