Synthetic Aperture Radar. What you're really seeing here is what happens when you try to put together a 3D image from an angled line scan from a moving scanner. There isn't enough information to do this perfectly, so you get artifacts on tall objects. You can see somewhat similar artifacts in Google Earth when looking down on tall objects for which they don't have full elevation data, like trees.
What's impressive is that they're getting 50cm resolution from orbit. Doing this from aircraft is nothing new; that's been going on for decades. But 50cm from a satellite? That's an achievement.
