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TF-IDF is referred to in a number of Google Patents as something that the search engine may use for stop words removal. It is the old method that used for document search many years ago.
I think it is so blindy to use this old method for SEO purposes.
In reallity BH SEO use more methods which do not constitute a risk for a website. Because these methods based on weaknesses of the ranking system. That is why you shouldn't worry about Google core updates or manual actions.
Some methods, like PBN or link bombing has lost their efficacy. Because these techniques based on old principles.
There's no denying that you can use BH SEO techniques without risk for a website... if it's done cautiously and slyly. But I half agree that you shouldn't worry about Google's core updates. They do exist and they do work, sometimes they sting painfully. Can you share with us your secret ingredient (or maybe a BH technique that works that well)?
I don't recommend use BH SEO because there are expensive and ineffective techniques in many cases. Often, it is better to invest money in the content or website optimization (I know cases and it works).
No, I can't share a BH technique :) As you wrote it must be done cautiously and slyly. For example we all know myth about using keywords in domain name or URL. Implementation of the such technique cost 300 USD and guarantees 1-3 position in the SERP in UK (ecommerce website) for years. I've come across it several times in my work.