Wise man has spoken "they aren´t spraying anything!".....we all better believe! 
Nobody HAS to believe.
What I'm trying to do is explain what is being seen is nothing more than a vapor trail.
If a sinister government WANTED to spray some dastardly chemical on a population that makes populations infertile, kills the weak or even worse makes them vote Republican a little bit a logic would tell a person that these things could probably be developed in something that could be completely invisible when sprayed and that such high altitude deliveries would be one of the poorest means of dissemination as you would have difficulty reaching effective concentrations on the ground.
If somebody wanted to do something like this they'd be far more successful attaching it to a fake taxi cab in the traffic congested areas of NY and CA, especially in the latter example where air pollution levels would function as a cap. Perhaps somebody is already doing this with "crazy spray" (it might explain Berkeley) to great effect.
The problem is people are lazy and don't take the time to understand very basic science and they lack critical thinking and reason. And this is why you have some of them believing some very silly things. And as a result a genuine sinister scenario is created, while people on the internet spaz out about chem trails, HAARP, government generated Swing Flu, fake moon landings and how Bush engineered the greatest conspiracy in history it takes time and attention to the truly threatening actions governments take every day like The Patriot Act, declaring the legality of using drones against US citizens on US soil without due process and forced participation in socialized medicine.
Governments are CONSTANTLY undermining the freedoms of it's citizens and forcing them to pay governments to administer services they could simply obtain for themselves without having to pay a bureaucratic middle man. But these issues require basic intelligence to understand and expose so instead idiots look in the sky and declare "What are they spraying up there?!?"
