The Virtues of Getting Vertical

As general search tends to adopt more personalization features, narrow focused search engines are becoming less viable. Meanwhile, “vertical” search engines—particularly comparison shopping engines, but also engines for travel and financial services-- are melding with vertical sites, adding the informational content, buying guides and consumer reviews that will encourage users to engage with and trust the sites. The results are an amalgam: not totally a content site, but not a straight-ahead search engine either
http://multichannelmerchant.com/webchannel/seo/6-08-06-vertical-search/