It's not only about illegal activities. It's about listening in on our personal coversations and having the ability to act against a person or group that the Government deems hostile to it's own agenda.
You and I are having a chat about our dislike of the government and we agree to start a movement against it. Next thing you know we're branded traitors. (don't think that's just being paranoid)
The constitution was created to prevent that very scenario but we're letting our Governments take it away with very little fight at all. (Canada is following suit in many ways)
Our childrens' safety and security has a price but not at the price we're facing. Our grandparents fought against this VERY form of society. Now they're gone and here we are all over again.