While Google’s Matt Cutts says it is not OK to sell links. On the other hand, Jeremy Zawodny, a Yahoo employee owns a personal blog that has been found to be selling links to those seeking to buy some PageRank juice. This is apparently OK as long as those links aren’t spammy and not hidden.
Matt Cutts suggests using the “nofollow” tag in these links to avoid any reference to the possibility of link selling. This, however, goes against the rights of the website owner who has the right to do whatever he/she pleases. Someone has to pay for the web services and everything is NOT free as many would like to believe.
Google would certainly like this practice to stop as it affects their relevancy algorithms. So long as a market for links exists, there’ll always be people selling. It’s simply the business of economics. Mike Grehan points to the rich getting richer.
Interestingly, it goes against their own set forth webmaster guidelines which advocates paying for submission to directories such as Yahoo. Arguably, these links are also human-edited. Paid links, however, do not necessarily translate to a lower quality site.