Federal officials also said the approaching presidential election was a cause for heightened concern.

"People suddenly have a heightened concern about their privacy being invaded," he said.

Investors have also taken advantage of opportunities created by the heightened concern earlier this year.

There also appears to be a heightened concern on the part of many Americans for the homeless.

This comes at a time of heightened concern over America's competitiveness.

That has led to heightened concern among some diplomats and foreign experts about how China might respond.

The 1996 directive was produced under the Clinton administration, at a time of heightened concern over environmental issues.

Others point to heightened concern over the President's role in the fate of the world.

"This could even help them on that front; there's going to be a heightened concern about safety," he said.

Making the concept work would be a challenge, especially in an era of heightened concern for building security.