The ScottEvest in the airport
"Actually they say it's perfect for air travel, you can carry much more aboard, and in security you just slip off the vest and slap it onto the scanner band."
Now this is a bit confusing, because the reason they have the x-ray machines is because there it is expected that there'll be metal items in there, and the x-ray shows them just what it is. (For example, I once had a Swiss army knife in a carry-on, and I had to send it via baggage claim.) So I think it should only be a problem if for some reason they can't identify an object and it might conceivably be a weapon. (Or perhaps if you're really being a pest.)
I also thinks that Scottevest would have heard about it if it were a common problem: