But there's also another fundamental difference: even if there's the expectation of removing all copies of the same exact file, it is "trivial" for MegaUpload to know, by using hashes. They do have access to all files, as it is in their servers.

For Google to delete all pirate links to movie X it would be much more complicated, and would put them on a position of being forced to be the internet police.

not if they have the encrypted content only, and the decode key is only in the hash portion of a url, which never goes to a server.

But i guess crafting a technocal "solution" to a legal problem doesn't work, since the law works off intentions, and how much money you pay lawyers...