Black hat SEO is defined as techniques that are unethical in order to manipulate the search engine rankings. So, is buying links unethical and black hat? Well, this has been a hotly debated subject for over a decade now and will continue well into the next decade as well. There are different types of paid links available today. For example, is writing a ‘guest blog’ and publishing it on another website consider to be a paid link (as you’ve paid the writer to write the blog)?
Therefore, it is a rather hazy subject area and defining what is black and white hat is probably down to the individual’s perspective and the context in which it is being used. My advice would be to tread very carefully when blatantly purchasing links as this practice is unethical and (hopefully) search engines will find the culprits and penalise them. The best quality SEO campaigns are the ones that look for ethical practices that will generate a return on investment in the long-term, rather than looking to slightly unethical shortcuts.