Imo it is not possible for google to detect properly spun content, it is not worth computing power it requires. They can do this using ngrams for example, but it is uses a lot of queries. And for example article spinner I coded beats this algo, so google cant detect that the content is spun. Manual spinning is also good but it takes more than 30 minutes per article.
Notice: Because of the 3 days free trial, we must use Paypal's subscription button even for a one-time price. Unfortunately Paypal has a bug that only allows you to set max 5 years for the subscription. So when you see Paypal's notice that your one-time fee is actually a subscription that will be renewed in 5 years, in fact it is not true, it is a one-time forever payment, NOT renewable after 5 years.

Our article rewriter is an advanced automated paraphrasing tool that allows instant online paraphrasing of any article into a unique content. Rewriting of content can help you greatly in avoiding the penalties you may suffer due to plagiarism. This free paraphrase tool does not require any registration or sign up, all you need is to enter any human readable written content, and you will get human readable rewritten content in the results.
The instant article spinner or paraphrasing tool carefully scans the article you enter, looking for all the words that it can replace with synonyms. All the words or phrases that will be replaced are colorfully highlighted to make them prominent and easy to identify. By clicking on each of the highlighted text, you can see the original word along with other suggestions, and you also have an option to add your own word. To restore the original text, just click the original word.
So it is pretty hard actually to achieve unique and human readable article, but with little twists it can be done. I needed my wordai account just for FCS Networker, but I figured out that Spin Rewriter will fit perfectly for me because of their affordable price. If you need article spinner just for seo purposes, avoid them. If you want to create amazing articles, yes they are very good ..but pricey as ****…
Quality readable content is key here. Google, for example, will recognize that people are leaving your site soon after arriving if they perceive that your site or blog is full of junk content. This is called "bounce rate." If your bounce rate is high, then people are quickly leaving your site. But for the sake of your business, to build your online reputation and brand, you want people to visit your site, stay for a while, and then keep revisiting over the long term.