What is Link Buying?

This SEOmoz article on Link Buying and its... believe it or not... benefits got me thinking about what exactly Link Buying is. First off, let me highly recommend you read the article, watch the video and view the comments. There is a ton of interesting information in there. Moving on now.

If you discard everything about the article and boil it down to the most basic issue, you are left with the question of "what is link buying?" No one really bothers to define this and we all have our own ideas. The following are my thoughts on the subject.

Link Buying is often used as a catch-all phrase for any link that you pay to receive. Within that realm you have the spam link buys and the gray hat link buys -- I call them that because I don't believe that kind is necessarily wrong and I will explain why later.

1) Spam Link Buys - these are links people buy from directories, in the footers, the sidebars, etc etc etc. These links are from not-so-reputable sites and are generally not cool. They are not based on relevance, content or much of anything other than trying to prop one's site up in the rankings. These are the kinds of links that Google will devalue or send your site back to the stoneage over.

2) Gray Hat Link Buys - Everyone talks about white hat and black hat SEO practices. Spam Link Buys = black hat and so on. We all know what that is about. I call these gray hat because, obviously, they fall in something of a gray area. These are the sort of links where you find a site with relevant content and use an incentive (money) to get them to link to you. Relevant content is the key there because the content must be relevant to your site. This is the sort of link that everyone wants; the only difference between this sort of link and a standard white hat link is that this is paid for.

So why am I not against the second sort of link buy? Simple, I don't believe it pollutes Google, Bing, or anyone else's index. If you are paying for a relevant link then it is still a relevant link. So long as the link is linking to and from relevant, quality content, I don't see an issue.