Allowing people to create links to your website isn't shady. Paying people to link back to your website on high-value keywords like 'justin beiber lyrics' from

Allowing people to create links to your website isn't shady. Paying people to link back to your website on high-value keywords like 'justin beiber lyrics' from blog posts on other sites to artificially inflate your pagerank is 100% blackhat SEO. The payment in this case was a Twitter post about the link provider's website.