DMAA safe harbor only applies if you are not aware of the infringing content. If you have a bunch of links to the same file and only take down one then you have no protection under DMCA and the standard 'greater-than $3k damages then go to jail' applies.

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.