What you just saw is the result of one YouTube employee's 20 percent project. It's widely known that Google encourages staff members to use 20 percent of their time working on a side project.
A poster on the YouTube forums from an employee going by the name of YouTube Pete said, "I'm the developer working on the stereoscopic player as a 20% project. It's currently very early, hence the silly bugs like swapping the eyes for the anaglyph modes. A fix for this is in the works.”
What do you guys think? Unfortunately we haven't been able to watch it in anything but "cross-eyed" mode because we don't have the old-style 3D glasses. Enlighten us!