Let's say you presented the person an article and asked him/her to re-write it in his/her own words, what is that person called? Copywriter? Ghostwriter? Whatever the person is called, where do you guys hire them besides on DigitalPoint? Perhaps an outsourcing website but which one?
It's generally unethical and may involve copyright infringement, depending on exactly how extensive the rewriting is and what it is that gets rewritten. For instance, if your rewriter simply takes a 500-word article and replaces 50 or 100 words with synonyms, that would very probably be copyright infringement. I say very probably, and not definitely, because whether it's infringement or not doesn't depend on a set percentage of copied text. There's also the matter of whether the copied portion is the most important part of the work, the part that's worth all the money. So if you want a definitive answer, ask a lawyer. But do be aware that rewriting can constitute copyright infringement.
I don't really call it thieving. I used to be a writer on a gaming site, and I'd always browse bigger more mainstream gaming sites for news, then re-write what they said and gave them credit for the find.