If you were writing a textbook on SEO linking circa 2001, you almost certainly would have included a chapter on web directories. They used to be the primary way of actively acquiring one-way inbound links, before content syndication, blogs, or the paid link market really took off.
Web Directories and SEO Links: What Went Wrong?
Fast forward a few years, and you’d have to rewrite the chapter on directories and web links. In fact, you would probably downgrade web directories from a chapter to a page or two. In the SEO world, nothing good ever lasts long, and so it is with web directories.
* Traffic. With Google more accurate than ever, there was no more reason to turn to a human-edited list of websites. A directory might get you one or two click-throughs a month–or none at all.
* Redirects. Once directory owners realized their link popularity was valuable, they started hording it. Overnight, many, if not most, directories switched their HTML links to search-engine-invisible redirects.
* Fees. Most directories started charging for inclusion, or at least, for inclusion with a link rather than a redirect. If the fees were...