Source: http://www.reuters.com/article/2014/07/21/cybercrime-confere...
http://www.qatar.cmu.edu/iliano/svc/meetings/PX/2004-09-21/s... http://www.cmu.edu/silicon-valley/research/tech-showcase/pdf...
The mundane (and thus most likely) answer is that the CMU lawyers wanted to pull it either because they want to sort out some sort of intellectual property first, or they're worried about some sort of liability.
A government agency that wants to stay a step ahead of the competition or of its targets?
What about the political dissidents who use Tor? They could be at risk of certain death if caught by the authoritarian regimes they live under. Without coordinated disclosure, the "researchers" might as well have been signing death warrants.
In fact: I'm not aware of a vulnerability research conference that does get nosy about this stuff. I even reviewed for Usenix WOOT one year, and we didn't vet research for "coordinated disclosure". Not even Usenix works the way you want BH to.
That's an odd construction...
Generally when you see some outside force trying to suppress security research and the presentation thereof, it comes from the companies who will actually have to fix the problems and deal with support calls (or companies who feel that security through obscurity is sufficient and are hoping to somehow suppress the information from ever getting out). In this case, that would be maybe the Tor Project, but they generally are very receptive to this kind of thing.
This is something that has always been legally murky, enough so that I feel like some technical people could decide that they didn't care and just go with it. More people under them might have as well, pulled along by sheer groupthink if not genuine agreement.
This attack was unique not in that it made strong claims, but that it had unusually specific strong claims that indicated some amount of empiricism. I feel like you could only reasonably claim that number if you actually tested it against a very strong network simulation (which doesn't exist for Tor) or the real network.
It's not like other researchers haven't done similar things to get results about Tor. There are a few workshop and academic conference papers that talk about results obtained by analyzing Tor traffic; this is technically wiretapping according to the Tor project, but previously it's always been mundane enough that nobody has gotten involved. This experiment might have compromised some people's very personal information, and it's incredibly public.
This is all really just an expansion of "they're worried about some sort of liability." In any case that's by far the likelier of the two; I can't imagine you could sell IP related to this.
I more or less agree that liability seems more likely, but I have no idea what the nature of the attack is, so it's always possible it's an offshoot of some other research they are doing which can be patentable. Alternatively, it could be that CMU procedure is to require approval for all talks for brand and IP protection reasons and he just hasn't gone through the proper procedure, so in the meantime they pulled it (rather than pulling it in response to an actual analysis of the talk). This last one seems unlikely, though, as you'd imagine there was no rush to pull the abstract (which contained no details).