Read some samples from ChillingEffects: http://www.chillingeffects.org/dmca512/notice.cgi
The host could simply claim another user uploaded it after the DMCA notice was received and the original link removed.
Presumably DMCA notices don't apply to future uploads as well? That would be almost completely unenforceable for a service like Megaupload.
Edit: Just a couple more proposals for such a system. First, the link re-creation could be conducted randomly at different times after deletion for different uploads, giving the impression that it is not the result of an automated process.
Second, a host could publish all the DMCA notices they receive, providing a plausible explanation for why all the content is 're-uploaded' soon after being taken down. Surely a host can't be held responsible if its 'users' take it upon themselves to almost immediately re-upload any content taken down by DMCA notices?
There is also a red flags test. If a reasonable person would be aware that the site is hosting files that infringe then it's not protected. And also you can't get direct financial benefit from it, you have to close accounts of repeat offenders, and some other restrictions.
Basically everybody knew Megaupload hosted warez, there were red flags, megaupload didn't take down links they knew were warez, and they made money off of it. Case closed. There may have also been legitimate use of megaupload, but they weren't covered by safe harbor and them being shut down is the law working as intended.
> you could combinatorially add random junk into the stream and circumvent that as well.
One could, like how people flip/speed up/record tv to get around youtube blocking, but it would take a lot of work and dedication to keep uploading your 500+ MiB movie rips over and over again.
But the existence of a copy does not tell you whether the uploader had the appropriate license from the copyright holder, or is the copyright holder, of that copy. Files do not fit into "legal" and "illegal" bins by the order of the bits alone.
Let's say I create and sell a software package. I upload it to my Megaupload account so I can easily access it later at another location.
Someone else uploads a copy they bought with a stolen credit card so they can share it on a warez forum. I send a DMCA notice of infringement requesting this copy be removed from Megaupload.
Should Megaupload now also locate all links to that file and remove them, including mine, which is entirely legal for them to host? Is Megaupload required to breach its contract with me as a paying user of their service, in good faith and violating no laws, in order to meet the DMCA safe harbor requirements? I think not.