Gord Hotchkiss wrote an article titled An Intimate View Of The World Through Google's Eyes on Search Insider yesterday. The article provides some excellent thinking on how Google's Universal Search and Google's drive towards personalization will mesh.
A couple of Gord's comments stood out for me: "I can't help but think that personalization will drive universal search", and "Google will be able to be more confident in offering a much richer and more diverse set of universal results when you can tap into previous search and Web history". I agree with Gord that personalization will do a lot to empower universal search, and vice versa.
At another point, Gord also indicates that he thinks that "universal search, in one fell swoop, makes the idea of vertical search irrelevant". I see the impact of universal search on vertical search a little bit differently. Improving horizontal web search will certainly impact certain types of vertical search opportunities. Some of these search properties may well be affected significantly.
But, I also think that vertical search is such a deep topic that universal search can't possible impact all of it. For example, there is a huge amount of vertical search in the B2B space. Outsell recently forecast that the B2B vertical search market would exceed $1.0 B in revenue in 2009 (not too far away!).
I also think that there are plenty of vertical search engines that use completely different contextual crawling methods, or use and integrate specialty data bases which are not easily interpreted by, or may not even be accessible by, a web search crawler. I suspect that borh of these scenarios will be unaffected by Universal Search.
However, as noted above, I also think that there are plenty of "thin vertical search engines" where the value add is pretty minimal, and these could be affected in a big way.