Is this just a defensive measure, or is it in response to hard intelligence? I suspect the former.
Probably just someone at the pentagon hit the wrong button :)
More fluff just in case there are lawsuits later on. What these morons call "heightened security" is just increased hassassment of American citizens, increased averted glances to avoid profiling, and measures that don't have any affect on thwarting terrorism. Have you ever noticed that they protect government facilities, but never more likely civilian targets?