We got ourselves a step-down transformer for Nigeria. It would convert their 240-V electricity to 110-V so our electronics would be in less danger of frying. True, AUN provides one, but it would be very nice to have a second.
The transformer is HEAVY. So rather than put it in our checked bags, we decided to have it in our carry-on. Part of the reason we had a 45-minute love-in with the TSA was that their scanner cannot see inside the transformer and they confiscated it. $60 down the drain.
Now, the agent insisted that we would be able to pay the $100 for an extra bag and send it through our checked luggage, but after the handling we had received I doubted he knew his own name without looking at his name tag. So I called up the TSA to ask. No, they said. If the scanner upstairs couldn't see through it, the scanner downstairs won't either. We'll confiscate it there too.
So instead we're going to make do with one for our first 3-5 months and ship ourselves a second one. But if any of our fellow travelers are thinking of carrying a transformer with them, be ye warned.