Off-topic: we (the human species) have built an AI that can master the game of Go, but we don't yet have the intelligence to publish charts correctly on the web. That blur of a JPG is half a megabyte!
I don't require the screenshot to be instantaneous, I require it to appear instantaneous. In that sense, if the whole rendering pipeline is working to give me a framerate of 60 fps, then I could spend ten times as much rendering a screenshot without that delay being noticeable. Also, why on earth does Windows (don't know the behaviour on Linux/Mac) apply ClearType to a screenshot? That has always bugged me, there are some situations where you tolerate it and others where it hurts.