Recent specific threats from Islamist propaganda broadcasts indicate Sin City may become a bomb target. It’s a deadly serious situation, but it brings up a local joke that has been around since the Cold War. Here it is:

If you’re on Las Vegas Boulevard and there’s a warning about a bomb attack, immediately run into a luxury resort on The Strip. Hide under any slot machine in the casino, because none of them will ever be hit.

Seriously, in Las Vegas and at all other world travel destinations you'll visit, keep constantly alert to possible terror attacks where large numbers of people assemble. Have an alternative plan when immediate danger is indicated, and be prepared to find safety in an emergency.