My former teacher, McCormick Professor of Jurisprudence Emeritus, and founder of the Princeton School of public law Walter Murphy was placed on a TSA watch list for scrutiny in flying. While the reasons for this are of course secret, an airline employee stated that attendance at peace marches often suffices, and that Murphy's speaking against the Bush Administration's policies could well have been the reason.
On the one hand, I certainly have doubts-- the airline employee may well not know what he or she was talking about (frontline airport staff are pretty unlikely to be in on the TSA's secrets); I find the idea of Bush administration officials paying close attention to scholarly writings and lectures in constitutional theory somewhat dubious; and, well, what professor of constitutional law hasn't criticized the administration at this point?, yet I haven't heard that the whole discipline is on the list.
On the other hand, we're left with no way to know, and no ability to get any competing story to the airline employee's... and the employee felt confident enough in having seen enough selectee-list cases to offer the generalization, which probably has some evidentiary value. And Murphy himself seems sufficiently persuaded to want the story to be known-- and I have very considerable faith in Professor Murphy's judgment and sense of things. Most disturbing.
See Murphy via Mark Graber, Jack Balkin (whose post matches my view on the whole), and Orin Kerr.
Update: The Wired blog seems to offer good reason for skepticism-- which is still fully compatible with everything Balkin said...