Adding an XML Sitemap to your blog is one way to ensure your blog is getting indexed by all the major search engines. And unless the content in your blog is getting indexed by an engine like Google, Yahoo!, Live Search, Ask, and others, it won’t be found by search engine users.
According to the Sitemaps website:
Sitemaps are an easy way for webmasters to inform search engines about pages on their sites that are available for crawling. In its simplest form, a Sitemap is an XML file that lists URLs for a site along with additional metadata about each URL (when it was last updated, how often it usually changes, and how important it is, relative to other URLs in the site) so that search engines can more intelligently crawl the site.
Web crawlers usually discover pages from links within the site and from other sites. Sitemaps supplement this data to allow crawlers that support Sitemaps to pick up all URLs in the Sitemap and learn about those URLs using the associated metadata. Using the Sitemap protocol does not guarantee that web pages are included in search engines, but provides hints for web crawlers to do a better job of crawling your site.
Since I have a WordPress blog, I use the Google XML Sitemaps plugin. After installing and configuring the plugin, my blog’s inclusion ratio – or the ratio of pages in a search engine’s index divided by the total number of web pages – has consistently hovered above 95%. The image on the left indicates that at present, Google has indexed 756 pages of LDS Media Talk.
Although adding a Sitemap to your blog won’t guarantee that web pages are added to a search engine’s index, it’s simply another way to ensure your blog is search engine friendly.