It's a high profile tech magazine with mainstream credibility. It would be silly for them not to have FBI sources.
For the record I'm one of the people who believe what the FBI did here is wrong. I imagine if they had know what it is and what it can do early on, they would've shut down Bittorrent Inc, too, for "facilitating piracy", "conspiracy to create piracy", "money laundering" (by making money as a company that creates torrent technology), and some other CFAA charges, for good measure - all of them bullshit.