Google does the same thing, but no one ever speaks up about that. Realistically speaking, if you don't want your content to be scraped by such services, put it behind a login page. We as content owners need to stop fighting against technology; it's not a battle that can (or should, really) be won.
Google provides search so people can find your site, and then sends people to your site.
Scribd do neither - they appear to take your content, put it on their own site, and provide nothing in return.
I, as a content owner, expect that a copyright notice should be respected, and I don't expect to have to track down every copy and sue the plagarists and thieves. I've certainly stopped providing PDF references to HN because they aid and abet such theft.
I'm not averse to technology, and I freely provide much of my written material for free, on my sites. I just expect to have people come to my sites to read them, and not have parasites like scribd steal the material without remorse or recompense.
So, let me see if I understand what you're saying.
What you're saying is that when I write something, and want people to read it, it's not enough to use the law and put a copyright notice on it.
What you're saying is that if I publish it, even if I've done what the law requires and marked it as mine, anyone can copy it and publish it without my permission.
Further, there's a company that will do this wholesale. They'll take loads and loads of other people's stuff, put ads next to it, give no additional indication that they didn't produce it, and make money from other people's work.