Many people install plagiarism tools that notify the owner if someone copy from their website. These tools search for the similar content on web and match it with the original.
Don't mistake that no one can catch you if you spin it. For ex. 1Text.com can easily detect plagiarism even if you spin it.
Secondly, if you want to use someone's content. Cite it and add you input as well. If you spin the content, means, you stole the original idea and paraphrased it. This is not professional.
However, if you want to go Black Hat way, protect your name.