Experts say that, while the major search engines are undeniably the most important target spaces for search engine optimization (SEO), online directory services like can be critical to maintaining brand identity online.

Lori Weiman, writing the Brand Aid column at Search Engine Land, points out that poor coordination with affiliates and clever competition can take a poorly optimized listing off the front page for online directory listings. Wellman also cites statistics saying that such yellow pages-type sites are growing in popularity, 23 percent in the last year alone.

Weiman advises careful search engine optimization (SEO) based on generic terms to drive localized search performance, saying that national brands tend to be less dominant in their SEO on local directory sites. In fact, in a local directory search for "mortgages," writes Weiman, only one nationally recognizable bank appeared in the search listings.

This could be because national brands focus heavily on the major search engines like Google, and are less likely to pay close attention to search engine optimization (SEO) in highly localized listings like the yellow pages.