Just to play devils advocate for a minute here...

What is to say that someone couldn't hang one of these up with some det-cord in it in the same places? From what I understand, these were devices with LEDs and batteries -- a evildoer could easily put some detcord around the edges there and have a pretty potent bomb... since these were hung up on bridges and whatnot -- it could be seen as a threat.

Yes -- they ended up being lightbrites this time, but when funky looking signs start showing up on bridges in my city -- I would expect the city to investigate. And let's not forget that Boston was an important city in that 2 of the flights on 9/11 came from Boston Logan airport...

Not to say that the govt didn't overreact, but it was a pretty stupid stunt.