You haven't provided any reasoning for why these requests need to be secret. People have the right to face their accusers, and by the time dumps of their online accounts are happening (akin to a search of their home), they should be able to exercise that right.
Are you suggesting all law enforcement agencies should notify a person or group prior to commencing an investigation? How amusing would it be if a detective turned up at your door and said "Oh hai! We'll be parked across the street in an unmarked vehicle for a few days while we observe your suspected illegal activities."
People have the right to Habeas corpus, they shouldn't necessarily have the right to know they are under investigation. In my opinion.
Passive surveillance is a far cry from having your home and belongings secretly searched. Standard procedure is not and should not be no-knock warrants to covertly sneak in while suspects are not home.
