This sort of thing worries me on more than one level. First I enjoy doing amateur science and already have enough problems with my neighbors thinking I am crazy let alone if the cops ever saw all the stuff I have laying about, nothing illegal just with the way things are today I'd have to do a lot of explaining. Second is the whole nanny state thing of it, that someone might get hurt, well life is dangerous get used to it. Third it's discouraging students from entering science which puts the future of the US in danger.
As far as terrorists go there are plenty other ways they can strike that don't involve any of this stuff remember the way the DC sniper had everyone in a panic. Also is a country like the US infrastructure is very vulnerable to rather simple things like trucks parked on the railway. You don't need a big bang just a big panic. A lot of small things spread throughout the country would have a greater effect because people would never know where it would happen next.