A cheap-and-nasty MD5 (for example) of the exact same film stored in different file formats will yield different hashes.
A more sophisticated hashing methodology (for example something akin to the audio-fingerprinting tech used by Shazam) might yield a match.
Could have MegaUpload have done more to prevent pirated movies from being uploaded on their servers? Maybe, maybe not.
Should they still be protected by the DCMA? IMHO, I think so.
Could MU have prevented "piracy" by blocking uploads of copyrighted material? Again, I'm inclined to agree with you and say "DMCA", there are too many privacy issues involved for sites to go jack-booting their way through everyones files (which again, Kim D-C mentioned in the video), especially when he's holding out an olive branch to the content companies by allowing them to delete millions of "illegal" files without any due-process.
This has been mentioned before, but I'll say it again.
If I upload Batman to my personal storage locker, and never share it with anyone else, and then a pirate uploads Batman and shares it with everyone, why should I lose my digital copy of Batman due to the actions of someone else?
Maybe I don't have a thorough understanding of now Hashes work, but if we both rip the same movie with the same software, won't that file have the same hash?