Well, let's be honest. The "humidor" pretty darn well resembles a very common depiction of "pipe bombs" in popular entertainment and in photos of evidence from public/publicized courtroom proceedings. It is not at all far-fetched to believe many people might see the "humidor" and reasonably (however erroneously) believe it to be the real thing.

But Boggie D brings up a good point. Many common items that appear to be benign can be (and are) used as IEDs. Who remembers the Boston Marathon bombings? Those were created using common ordinary pressure cookers. Had those IEDs been clearly visible (they were detonated while covered by backpacks) it is highly likely that while someone might have thought it odd to see a pressure cooker in that location they probably would not have thought them dangerous (in contrast, residents of Israel and other areas where security is a high priority) are trained to be ever vigilant for items out of place and not consider anything benign until proven so; not the case at all in the US). And contrary to arguments posted above, there is no requirement that an object have visible wires for it to be considered an IED.

Boggie - assuming it is metal and can withstand higher internal pressure than the PVC, your thermos container will probably make for a much more effective IED than the pvc humidor. But your thermos does not at all fall into a category of items resembling objects that many people would likely perceive/identify as being an IED. So once determined as being benign it is allowed through the PSC because it is not at all likely to be perceived as an IED. Whereas, the thing that resembles common depictions of a pipe bomb are not allowed.

I am with the TSA and dept of homeland insecurity on this one.