Via Boing Boing, here is an awesome photoessay by Russell Davies on playfulness originally delivered at the Playful conference in London. From the essay:

Everyday Pretending is something you do with a bit of your brain, with the edges. It’s a thing of inattention, not concentration. Compare, for example, the Theory Of Fun piano stairs with Greyworld’s tuned railings. The stairs thing is fun and it makes a point, but it would drive you mad after a while, there’s no subtlety to it, no joy in the discovery, nothing hidden, it’s all on the surface. It’s that totalising instinct of so many ‘brand’ people – make things obvious, make things clear. There’s a parallel in the maniacal world-building instinct of games people – leave no detail unturned, offer no escape from the vision … We don’t need many cues to help us pretend. We’ll find meaning in the noisiest noise – just give us a tiny signal and we’ll come up with a message.