Do we Trust our own Government?

Through all our discussions in American History, I feel like a people have a general distrust for the Government. Whenever there is talk about the limitations of Civil Liberties, people act like the Government is out to get us. I wonder, why is that? Isn't the Government here to protect as, are we not a Democracy, for the people by the people? If we in fact are, then why do people have a fear of our Government and what it can do? I think that if they want to wiretap our phones, why should we oppose them? Shouldn't they be doing it to keep us safe? Shouldn't limiting free speech be something to protect us, rather than being a tool to suppress and control us?  My main question is, is there a reason people distrust our Government so much and are these reasons justifiable? We elect these people and they are Americans like us too, why should they be feared?