Call 911 for help when your life is in danger and the dispatcher might forget to call you back or might say, "I really don't give a sh*t what happens to you."
Call 911 to harrass two peaceful protesters publicly expressing a political opinion you find offensive and not only will the police be sent to investigate, but they just might collaborate with you and the State's Attorney to have the protesters wrongfully arrested and maliciously prosecuted. You may have to lie and say the protesters are, "acting like they're throwing stuff".
Don't worry though, it's only illegal to make a false report to 911 . And everyone would agree that people should be arrested, jailed, and forced to defend themselves in court against criminal charges that are based on nothing more than a person's baseless claims.