Las Vegas is a target...
...because it is another symbol of our "loose" great-Satan morals. (Which didn't stop the suicider-pilots from stopping by for a bit of pre-virgin sackdances ;-)
It could be the FBI simply wants to flush out the terroists by posing in a disbelieving stance.
A wait and see approach is wise - but ALL major cities, with anything of interest or reknown on a global scale, should since 9-11 always be on high alert and keep their guard up..and the highest alert on our national birthday.
SDAI-Tech1