1. Raise precautions. Protect Americans. 2. No essential change whatsoever to Governments and military will do, just a warning to the public. 3. Trade attack for credit. If attacks go with the way the alert goes, credits are earned. If attacks go against the way the alert goes, credits are lost. 4. It is a smart psychological strategy. Attackers tends to attack when alert level is low. We raise the level at important days, and the likelihood of attack decreases. So piss off the attackers.