A normal system admin might decide a single 4gb file accounting for tens of terabytes of traffic is unusual and investigate the cause. Odds are pretty decent you'll be able to find a source driving all the traffic.
Kim Dotcom is going for the blind eye approach. Just close your eyes and cover your ears so it's not your fault. He did this with MegaUpload to the tune of hundreds of millions of dollars of profit. I wonder if the new site will reward users who have highly downloaded files like his last?
Can you prove, or disprove, that the cryptography was intentional broken? Doubtful. Can you prove a website didn't try to prevent the mass sharing of copyrighted material? Yes. Is that illegal? Maybe. Should it be? That's whole 'nother can of worms.