It's not just payment. Google also considers an unnatural link profile as evidence of spammy actions. This is perhaps reasonable in isolation and in most cases

It's not just payment. Google also considers an unnatural link profile as evidence of spammy actions. This is perhaps reasonable in isolation and in most cases. But it certainly raises the possibility of negative SEO, where you point large numbers of spam links to a competitor's site in order to blacklist them with Google. See this for example: http://moz.com/blog/a-startling-case-study-of-manual-penalties-and-negative-seo http://moz.com/blog/a-startling-case-study-of-manual-penalti... I run a site that has received a few tens of thousands of visitors. I checked webmaster tools. I have a bunch of spam links from btclush.com, marqueefy.com and some russian sites. I can't actually find the linking pages, btclush.com itself is blank and all content is on subdomains. It's not clear to me what I, a small webmaster, should be doing about this. I'm hoping these sites send spam links to almost every site – in that case presumably google is aware that site owners are not at fault. I don't have the time to contact spam sites to tell them not to link to me or to disavow all these links. Note that the composition of the spam links changes. The last time I checked different spam sites were linking to me.