I've had the ...whisper, whisper...suspicious look...whisper, whisper...call the supervisor over thing...followed by the body search, full inspection of the light and lots of questions. But TSA has always been polite and understanding. Sometimes they recognize immediately that it's no threat. They never have disallowed it.
I actually was just refering to the fact that when I take an HID can light on any journey I simply have one more thing to watch out for. Because of their inherent fragility and the fact that they're so expensive I feel that I have to take extra special care. I carry mine on. Which means not only do I have to use a bit larger carry on bag but I also have to be extra carefull with it...you know...to avoid bumps and bruises...that kind of thing.
But then, again, I'm pretty particular with my goodies. For instance, while riding in a truck along the bumpy jungle roads in Akumal, where do you think I put my can light? Not in the back with my other gear...no way. It sits in my lap! You see...I probably worry way too much about the darn thing. Oh, ya...on the boat...I don't leave my can on my belt with the light clipped up like you yahoos...I saw that photo, Bob...I take mine off and store it in a safe place. I know...I'm sick.