Doesn't Princeton lock-down their network tighter than a frogs asshole? If I'm not mistaken, recent news reports suggest that Princeton blocked all Android devices from their wireless network due to a bug that prevents Android devices from properly releasing assigned IPs after they expire. I believe Princeton also blocked iOS devices for a similar reason further back in history, before Apple fixed the bug. So, unless these news reports are mistaken, clearly some institutions DO block-out devices based on the OS they run. Maybe it's automatic, or maybe it's rather manual. Even if you have to call-in to the IT department and request they add your MAC address to a white-list and specify which OS you run at the same time, lying and connecting a Linux machine is a pretty stupid reason to get expelled from college.
That said, I'd have to imagine that if any IT department DID limit the wireless network to only Windows machines, this would be a clear indication that the head of the IT department was somehow getting kickbacks from a regional license vendor. The reason to allow Linux on your network is clear, it's Free. Except for private colleges (like Princeton), most colleges don't have the extra money to afford huge numbers of licenses for the thousands of computers they have sprawled around campus (even with site-license and educational institution discounts). At my alma mater, even most of the computers that did have Windows could also dual-boot to Linux (Redhat was the flavor of choice at the time). The only exceptions were department-run labs (like the Mac lab run by the C.S. department, and the engineering lab run by the E.E. department).
And no, I don't buy in to Microsoft's whole "Linux is more expensive than Windows" argument, especially at a college where most of the IT staff consists of students employed via work-study (assuming this isn't some arts-only institution).