Hiding redundant elements, navigational bars, maybe images, etc... is fine, but I'm definitely not comfortable with the idea of hiding content based on context.
Besides, I thought the point of responsiveness was to REARRANGE data, not completely eliminate it. styling, yeah, go ahead and get rid of elements and color bars and what have you, shrink pictures, but please don't throw away words!
http://www.w3.org/TR/css3-mediaqueries/ "Among the media features that can be used in media queries are ‘width’, ‘height’, and ‘color’. By using media queries, presentations can be tailored to a specific range of output devices without changing the content itself."
The part "without changing the content itself" is pretty clearly not what he is doing here. Like dozens of others have said, just an interesting idea but not something that should be used like this in practice.