Meh, the Government/FBI has bigger shit to worry about than to catch "pirates".
Do you even know how many people download music? I mean really...think about it.
Plus, think about this.
Why did Apple allow the iPod to play .mp3 files, when the ones you download from the official store is .mp4? Hell, all the songs you download from the store is .mp4. Because they knew people would download music and put it on their iPod. They also put a stupid sticker on the plastic outing the iPod comes in that says, "Do not steal music." so they can come back and say we warned you.
There's millions of pirates out there. Trust me, if the FBI wanted to shut down all the torrenting sites, all they would have to do is type in Google, "Torrents".