This is a proven maneuver and Cogent is not the first to do it.
i guess that without knowing who else these de-peered networks are customers of, it's hard for an outsider to guess which ratios into cogent's network by other peers will improve as a result of de-peering these networks. had you been writing for a technical audience i'm sure you would have alluded to this, i'm sure. now that i know the article was a leak rather than a publication, it all becomes clear.
... That full explanation was missing from the writeup that is posted (and I'll allow it to stay up for now), because that report was aimed at folks who may not be fully conversant in peering - financial professionals. BTW, thanks for dropping me an email to ask me about it, before posted to NANOG.
the text i saw was so uncharacteristically non-dan-golding, that i really did think it was a hoax. you're right that i should have asked you about it; in my defense i was leaving for the weekend and didn't have as much time as this should've gotten.
As far as reachability from one provider to another - I've heard that one can make routing changes quickly and easily on this crazy Internet thing. Perhaps in the 24 hours since I wrote that, a few changes occurred?
i'm a cogent customer, and my path to nlayer at the moment i read your note still went through cogent. what was i to think? anyway, problem solved.