How exactly are rights holders required to inform MegaUpload of content to remove? Every DMCA takedown request I've seen generally has a collection of links. I

How exactly are rights holders required to inform MegaUpload of content to remove? Every DMCA takedown request I've seen generally has a collection of links. I don't know the letter of the law of the actual process, but the ability of a rights holder to tell MegaUpload to take down all copies of X piece of media seems... Unfair. Not everybody has a hash based system, and even if they did, variance - such as raring, modification times, etc, would make everything mismatch. And, if that is actually the process, why do they bother to include the links at all?