"They don't spy on us or listen to us all in real time, what they do is monitor (they probably have some form of A.I system doing this) emails and telephone calls for certain key words/phrases, these emails and calls are then stored .. perhaps they will never be listened to again, then again if you're a person of interest or at a later date you begin to become a problem they can start to collate this information and see if they can find something that could be used against you."

Author : @perceptualflaws

Just to handle 10% of the key words looked for they would have to have more people working in there computer rooms going over this stuff than all the governments and agencies they currently have working in the world. It is a boogie man that is way more effective than if they actually tried.