Good article from Forbes on the on-line travel business
Currently, the online travel business has evolved into three distinct groups of Web sites.
With online travel agents, like Orbitz and Travelocity, users buy tickets directly from the site, which acts as a middleman and maintains customer relationships. There is also a new generation of travel search sites, or "meta" travel sites, like Sidestep, Kayak or Mobissimo, which find and then refer you directly to airline and hotel Web sites for booking. The last group is old-line travel guides--content oriented sites, like Fodors.com and LonelyPlanet.com, which are increasingly being threatened by user-generated guides, like Realtravel.com and Expedia's Tripadvisor.com.