Warning: The content below in controversial... My friend, Dave, has been doing CB and SEO for a long period of time. He currently owns more than 20 niche sites for various CB products. According to him, it was really profitable by targeting product name keywords using churn and burn method. Until the beginning of 2016 when he saw a sharp decrease in conversion rate. Then, he noticed there is an increasing trend that more people are starting PPC campaigns which are directly targeted on CB product names... You may have a try, when you type a CB product name in G, there must be lots of ads showing "exclusive bonus" for the particular CB product. You gave a lot of effort to gain a higher rank, but the SERP is simply "hijacked" by those ads, so you want to remove those ads in the SERP, so as to increase the real position of you site. So what you will do... My friend, Dave, he just told some of his friends who are "interested" in the "exclusive bonus" for the particular CB product and ask them to CLICK ON THOSE ADS to see if any real bonus. At the end, there is no real exclusive bonus and no purchase is made by Dave's friends. But the advertisers have to pay for their PPC expense, so eventually they made a loss for their PPC campaigns. The end result... Those "unfair" PPC campaigns stopped and Dave's sites have higher search engine CTR and conversion rate again.