LinkI know LJ isn't exactly a decent source for this info, but I can't find the original site I read it on and their own sources are at the bottom of the post.
As I mentioned in another post, file hosts do have a decent defence behind not clearing out their files of illegal stuff. Sure, they know people are going to use their servers to host illegal files, but there's not much they can do about them unless they're marked "This is an illegal file, delete me".
It's too easy to change the various values used for checking a file size by simply RARing a file and adding a txt with random characters in it, so simply deleting every file with the same CRC and/or filename isn't going to cut it.
You could say they could go through them manually, sure, but that'd take a tremendous amount of effort and manpower, and by the time they were done (and it would take a LONG time) there'd already be files replacing the ones deleted at the beginning of the process.
Hell, I have enough trouble deleting multiple copies of the same files on my own PC when I've downloaded one as a plain file, another in a RAR, and another in a different format.
It's obviously not a be-all and end-all argument and defence, but it's not as black and white as "they host illegal files, they know it and they just don't delete them." Just like some say piracy isn't as black and white as everyone states.
Of course, following MegaUploads' example and buying a yacht or two with the money you make from it... not so "shades of grey" anymore.
[Edited by Skyheart, 1/24/2012 4:04:00 PM]