Ryan Sager raised a minor stir earlier this month with a TechCentralStation column (building on posts from his blog) criticizing (non-hawk) libertarians' "unseriousness" on foreign policy questions. Radley Balko has written a lengthy and effective response.
While I'm in broad agreement with what Radley says—Sager, his own protestations notwithstanding, seems to want to use "serious" as a rough synonym for "agreeing with Sager"—I'll actually stick by a shorter response I sketched earlier on my own blog: If libertarians don't seem to speak with a unified voice vis a vis foreign policy strategy, it's because they shouldn't be expected to. Not because individual libertarians might not have plenty to say about how to efffectively fight terror, but because there's not likely to be anything distinctively libertarian about the relevant proposals, even if some proposals are clearly unlibertarian.
Domestic crime policy provides a good analogy. Libertarianism as a political philosophy has lots to say about what sorts of things shouldn't be crimes at all (prostitution, smoking pot) and about what methods of fighting genuine crimes are inadmissible (warrantless searches, coercive interrogation). But when it comes to the best way to reduce muggings, say, libertarianism (as opposed to particular libertarians who may have relevant expertise) isn't going to have a whole bunch to say. Do more police patrols work, or is the marginal dollar better spent on more streetlights? How long should sentences be to provide optimal deterrence? Invest in undercover agents to infiltrate gangs or better forensics technology? These are choices made by governments, but they aren't really political choices; they're technical ones.
All this notwithstanding, there are probably some distincitvely libertarian things to offer even on these sorts of questions—Radley links quite a few papers by his Cato colleagues. Even on strictly instrumental questions, someone of a Hayekian bent is likely to come up with different pragmatic solutions to any number of problems than someone who believes centralized action is more effective. But we shouldn't expect the same level of consensus at this tactical level that we find on broader questions that lie closer to basic political principles.