Jon Payne writes about the need for directories subscription in Search Engine Optimization process. He claims that one should submit its website only to the main directories, and more specifically to theme-based directories.

"Anyhow, theme-based directories offer the ability to really provide more detailed, industry-specific information. They also seem to lend themselves moreso to actual human editing, which generally results in higher-quality results and thus a more useful directory." says Jon Payne.