SODAssault linked to the first thing that occured to me as well, this reminds me vaguely of the "Aqua Teen Hunger Force" debacle a few years ago.
That said when I did my anti-terrorist training for the casino I saw a few videos of being getting blown to pieces to demonstrate exactly why the threat of bombs should be taken seriously. Of course after getting us all certified for the books, our management proceeded to pretty much ignore all of it (which is to be expected when dealing with what is functionally a dog and pony show).
From my perspective it's pretty awesome that someone is actually taking this kind of thing seriously. Bomb threats are one of those situations where you get treated like an idiot for doing the right thing and inconveinencing people when nothing happens. However it's that one in a thousand situation where it's bomb that people are actully thankful, or where one goes off and people then start screaming "OMG, why didn't anyone do anything?".
People do hide bombs in things like toys, or even on people. Indeed one standard technique for a lot of cultures where children are a bit less valued is to load the children with bombs, or carrying toys loaded with explosives, and then use them as a delivery system. This is done to Americans in paticular because we, even among civilized Western Nations, have a certain reputation for the way we treat and react to children. That whole "Sea Bees Do" statue outside of Arlington sort of says it all, and people around the world realize that blowing up kids is going to have a psychological effect on us that goes beyond that of most cultures (who would also be upset) in addition to what the bomb does. This is not to say that other countries don't care about their kids, but consider that we get freaked out a lot more by the norm when we see things like "Saddam's Lion Cubs" in the prelude to Iraq, or the child soldiers of Africa, even if we should be used to the idea after having dealt with groups like "The Hitler Youth".
It's also noteworthy that a lot of "professionally" coordinated bomb attacks are going to be based around what is called a secondary device. That is to say that you set up one bomb to to damage, or something that looks like a bomb but is a dummy. The idea is to get emergency services to show up. The thing is that emergeny services tend to set up in safe locations away from the suspected device, but with a good view of it. Someone with similar training (or who knows it) can predict where the emergency services are going to set up, and a lot of the most well coordinated attacks will have a bomb hidden in the most likely seeming area(s) to be set off when they arrive. The point of the attack being to kill the cops/ambulances/etc... for maximum effect.
A point made when I was taking the classes, and we were presented with a hypothetical situation with a map, and told where (as a class) we were going to set up our command post to deal with the problem. We had a very quick, universal consensus, then the instructor pulled out the second sheet behind it with a picture of an explosion and the words "secondary device" by way of introducing the concept. You can never be psychic in situations like that but the point is that you should rarely set up in what seems to be the most ideal location unless somehow you know it's secure (which is nearly impossible in an emergency response). This is incidently why so many people accuse cops and other people of being idiots when they set up in an inconveinent location (to everyone else) when "a moron can see there is a better place right over there".
All rambling aside, I don't think this was an overreaction, especially not today. What's more I hope they have a word with whomever set this up because I think the intent was to get attention, and I don't think it's paticularly funny. I've never dealt with a real bomb in person (though I have responded to the occasional possible device, and secured areas and ignored far more of them on orders), but I've seen people get blown up by bombs on training films, and I don't think it's funny.
