"The animation curves on the Blackberry Playbooks UI are those of a predator, just as it pounces its prey; slooow and then fast!. It’s incredibly disconcerting, causing our lizard brain to subconciously analyze the motions of something as harmless as windows on a screen for signs of danger … interaction design should for the most part be all but transparent to the user, so here’s my pro tip of the day: try not to emulate our natural predators."

The Binary Bonsai

(Source: binarybonsai.com)