http://www.schneier.com/blog/archives/2009/09/immediacy_affec.html

“One of the things we know about how emotional reactions work is they are not very objective, so people can get outraged or become fearful of what might actually be a relatively minor threat,” Van Boven said. “One worry is some people are aware of these kinds of effects and can use them to manipulate our actions in ways that we may prefer to avoid.”