Thanks to Dave Munger on ScienceBlogs, it is now possible to understand why and how a cube can be seen in two different ways.
The first cube (A) is ambiguous because it can be recognized in two different ways (either cube B or cube C) and this perception can change from time to time if you keep looking at it. It’s not a perceptual illusion per se, but a visual reconstruction by our brain. And this same process is often used by optical illusions.
Now, “Seeing shapes in two different ways: how and when it happens” is a good paper trying to give us a better understanding of this phenomenon and even showing a video to support the explanations.