I want to elaborate on last week's message that we are moving towards two-tier searching, with general search engines "handing off" searches to more specialized search engines and databases.

This prediction is based on my belief that general search engines are not and never can be the single best way to access all information. That's especially true when you don't have access to all information anyway, and the information you do have is highly inconsistent in structure, depth and currency. Layer on top of that the technological limits on full-text searching, and you can start to see why I say this. Interestingly, the hot new search engine start-up of the week, Kozoru, reportedly raised $3 million in venture capital based on the concept of introducing taxonomies into search. This says to me that others are seeing the limits of keyword searching.

The opportunity in second-tier search is to take a specific subject area and cover it deeper and better than a general search engine ever could. This could be expressed as a vertical search engine (take a look at GlobalSpec), a vertical buying guide (look at Hanley-Wood's ebuild.com or Martindale-Hubbell's lawyers.com) or a vertical portal (look at West's findlaw.com). The commonality in all three of these sites is a tight vertical coverage area, proprietary content (if only because the content is stored in such a way that it's invisible to the major search engines), and lots of structure to speed searching and provide precise and consistently presented results.

I suggest that the major search engines will increasingly "hand off" searches to second-tier information sources. That's not to imply that these hand-offs will be free. I suspect second-tier information sources will assume that role through aggressive and expensive pay-per-click programs, and we're already seeing some very expensive exclusivity deals between search engines and specialty buying guides.

This game will get more expensive and competitive before it's over, and the rules of engagement are likely to change over time. Indeed, the general search engines may choose not to explicitly acknowledge that they can't be all things to all people, but this evolution will be hard to stop, because it's logical, natural and the revenue the general search engine might be forgoing is revenue that might never have been theirs anyway.

Is what I am describing the same as what is now being called "vertical search"? Yes and no. Two-tier search includes buying guides and directories, whereas vertical search generally refers to vertical versions of Google. Further, the word "vertical" still sends shivers down many spines, due to such things as vertical portals (ahead of their time) and VerticalNet (out of their minds). Two-tier searching is here already and working quite nicely. What's evolving is the relationship between these specialty search resources and the big general search engines. The better that relationship, the better the prospects for the second-tier search engine.