I remember reading somewhere that the policemen in the raid did not know what were going on, or even who the target was. I wouldn't be surprised if they thought they were taking down a terrorist cell, given that the personal used was the counter-terrorism special tactics Group.

Reading the Wikipedia article about the task force, their job is in dealing with high risk situations involving armed offenders and possible terrorism related events. They also train with New Zealand Special Air Service Commandos. In that context, the raid makes much more sense in how it was conducted, with silencers, helicopters, dogs and 20-30+ personal. The real question then comes to who in the command structure decided to use such group for serving a warrant, and collecting evidence for an assisting copyright infringement case. Given the nature of the crime, the low threat level (admitted in court), this is rather uniquely in history. One might also wonder how much influence the FBI had in the decision.