I think the plausible deniability comes from the fact that just because a certain pattern of bits happen to occur in some movie does not mean they ONLY happen in that movie.  In fact, that certain pattern of bits by itself is nothing more than reasonable use or a short "quote" at worst and at best simple free speech.  If the RIAA and MPAA claim "ownership" of "all patterns of bits from any subset of any format that encodes their copy righted works" then it could be argued that we are all guilty already by pure random chance!  Besides all files could be encrypted before being "chunked" and thus there is no way to identify a chunk with a movie. 

I think the BIG IDEA is how to solve the problem of "dead torrents" where no one has incentive to seed.  Enabling a bit coin payment system for seeders would solve this problem.  Eventually this will make bit torrent practical for all hosting and not just "popular hosting".   Less popular items would simply be "more expensive".