If you're a conspiracy-minded crackpot who uses "follow the money" reasoning, then another obvious possibility is Verizon or AT&T.
Why?
Every time one of these bomb-threat incidents happens -- and they've been happening multiple times a day every day for quite a while now -- Pitt uses their emergency notification infrastructure to coordinate communication about them. And that means text messages to thousands of students.
(Because of the whole "in loco parentis" thing Universities have to deal with, and because of the aftermath of Virginia Tech, and for all sorts of other reasons some of which Bruce Schneier recently articulated talking about this very topic, Pitt does not have the realistic option of scaling back their response. The minute they react less seriously, they're potentially open to massive lawsuits -- and that's if nothing happens. If the jackasses are waiting for a weaker response before doing something real, well, Pitt might not survive the aftermath.)
Reports indicate that multiple students who didn't previously have unlimited texting plans have now been forced to upgrade to unlimited plans. Follow the money...
Of course, that theory for what's going on is absurd to the point of being laughable. Can't be disproven, no, but come on...
It's almost certainly the case that some drunk undergrad asshat thought it would be funny to make a bomb threat anonymously, figured out how to push the buttons on the anonymous remailer while sitting in a public library, and did it. (Well, once the "scrawled on the walls of a men's room" vector had been shut down, which is how it all actually started.)
Let it spread to the level of a minor in-joke meme among even a small number of such folks, and you'd observe something an awful lot like what we're actually seeing now. Much more likely than government conspiracy, anti-occupy conspiracy, or mobile operator conspiracy (though of course we can't disprove any of those).
Until the masses of American citizens, especially and particularly the "helicopter parents" of current undergrads, are willing to accept a security environment that involves cost/benefit analysis and the acceptance of some actual threat, what can be done? And it doesn't look like they're ready to accept that any time soon. "Think of the children!"