Microsoft Corp. has announced plans to acquire Medstory Inc., a vertical search engine (VSE). The move by Microsoft can partly be attributed to Google's approach. The search giant recognizes health-related searches, then gives users the option to look for treatment, tests, symptoms and causes. According to a Pew Internet & American Life Project study, 113 million adults in the U.S. have searched for health information online. But the underlying driver for Microsoft's acquisition is the rise of VSEs.

VSEs are classic examples of targeting the Long Tail of search, as they are highly specialized and focused on returning relevant results for niche search queries. A classic, or horizontal, search engine relies on algorithms and crawlers to provide results. Whereas a VSE is created by users to return the most relevant results for their niche - these users know what their peers are looking for and know what sites are going to be the most useful. Outsell reports that the vertical search market will reach $1 billion in revenue by 2009.

While VSEs have a long, long way to go to catch up with Google, Yahoo and MSN, this acquisition is a sure sign that the big boys are paying attention. As more VSEs gain momentum you can bet they will be absorbed into the mainstream of search - as the Goliath's of search are forced to up the ante for the relevance factor.