Out of desperation, I used to work for one of these SEO companies. I was tasked with requesting removal of the their attempts at comment and widget spam from blog owners they’d flooded in the past.
After this became largely futile because the blogs had largely become abandoned or the owners refused, the next “strategy” was paying deadbeat or foreign writers $3 for 100-word “snippets” tenuously related to their clients’ business. Eventually I snapped and said that if we were doing something we’d be afraid to reveal to the search engines, then we probably shouldn’t be doing it. Addtionally, it’d be easy to see that the snippet sites had identical outlink profiles to our inlink profile.
I was fired the next day.