Blame Canada: RIAA spokesperson Amanda Collins seemed unaware of the situation in Canada. "Our goal is deterrence. We are focused on uploaders in the US. Filing lawsuits against individuals making files available in the US."
Which will be a colossal waste of time because in Canada it is expressly legal to share music. If the RIAA were to somehow succeed in shutting down every "supernode" in America all this would do is transfer the traffic to the millions of file sharers in Canada.
I admit, I always thought the blank-media levy was obnoxious, but hey, it seems like it might have unexpected advantages. There is still the problem of fairly distributing the proceeds, of course.