It originally was written two years ago, so some things have changed. But in general, it is still correct: for most browsers, you need to combine several ugly technics to get suitable results. Though, the quality will have nothing common with quality when you have direct access to hardware.
He's scaling images down, not up. Think taking an uploaded smartphone picture (multiple megapixels) and scaling it down to thumbnail-sized images for various screens.
ic - I thought it was just the usual image-downsample-and-upload thing you see everywhere.
even so, if the service is hosting your images in multiple resolutions you could do it all client side at upload time. they'd be trading bandwidth for cpu time.
you ever consider pushing the work entirely to the client with a resize implemented in javascript? that would cut down on bandwidth as well.