I blame them becuse they don't verify the content they post. Your criteria is a bit soft.
Everyone knows that there's malware on the net and it is the uploader's duty to avoid it.
I'm uploader on a few 4*-5* boards and I check the stuff I download to make sure it is clean.
Besides, I have a few trusted sources.
I do upload for money, but I play by the rules and anyones who wishes to be uploader ought to do the same.
And FYI, I'm not a site owner, not even a mod.