Why Google Webmaster Guidelines Dislike Websites That Sell or Exchange Links

Sam react to this post where a website was banned for selling Text Links:

What? thought I. If that’s truly what Google did, it’s way beyond any evil John Chow might have perpetrated. (Think of this in terms of competition. Google has AdSense. Text Link Ads is a competitor in the online advertising market. If websurfers continue to rely on Google for search results, and Google de-indexes sites for using ad services that compete with AdSense, then AdSense becomes the only viable option, in essense, creating a strongarm monopoly.)  Link