Installed one on my bike last year. Shortly afterward, some cool kid in his jacked up Dodge truck came riding through the neighborhood blowing his air horn when he felt like it. Which after about the fourth blast, was bordering annoying. My street makes a circle and he was making his way around the back side, still blowing.
I fired up my bike and pulled it up to the gate of my privacy fence and waited for the annoying little sh*t to come by. He came by in the direction that put the drivers window about seven feet from where I was sitting hidden by the fence with the bike off. As soon as he was directly in front of me, I laid on the Steble. Scared the living crap out of him and of course he got pissed and proceeded to tell me what a stupid MF I am. Long story short, when he left he didn't blow his horn anymore and hasn't been back.
The only thing I watch now is blowing it when I am in a cars blind spot. You don't want to be riding the line because there's no telling which way they are going to jerk the wheel when they here the blast.