I'm not sure I would term these ten ideas "counterintuitive"; in fact they come off as rather obvious, apropos the modern web. Maybe I'm in the minority on this but it seems like even just visiting SO a couple of times you get an impression for how and why it works and that seems to have been applied more broadly, e.g. Quora, to carry on with the Q&A model. Clearly treating this kind of thing as a social game is the root of the success of social news, for instance. Possibly this is just the benefit of the hindsight, nonetheless, certainly today they aren't counterintuitive?