This isn't just happening in the US anymore. My wife flew from Ottawa to London, Ontario with our two kids (2 month old daughter and 2 year old son) last July. They made my son take off his jacket, hat and teddy bear, put them through the x-ray, then wait on one side of the metal detector while my wife went through with our daughter. At that point he starting crying and trying to pull away from the big stranger forcefully restraining him from his mom. After verifying that my wife and daughter didn't set off the alarm, they waited for all the items to go through the x-ray. Only then did they sent my son through the metal detector, on his own. I got to watch the whole scenario from the dining area on the next floor up, and I've never in my lunch wanted to just hit someone as badly as I did then.
Can anyone venture a plausible reason why they couldn't have sent my son through with my wife, and then just scanned them individually in the event that the detector went off?