The idea
This act allows for secret intrusion into the lives of individuals without them being aware. It is a violation of fundamental privacy, often without due cause. At the very least everybody who has been made subject to covert surveillance without any evidence been found upon them should be advised of this having taken place and advised of who sanctioned such a procedure and why.
Why is it important?
Because people can and should be trusted. If we undermine freedom, we undermine peoples ability to take responsibility for themselves.