The personalization of search results is not the only way to target someone, you can also personalize your website to ensure your visitors feel engaged as soon as they arrive.
Gordon Hotchkiss gave some great examples and data behind personalized search and proved that I actually does work. Everyone remembers the golden triangle right? It shows how people use Google and where they actually click. Now, with personalized search and universal search enabled, the golden triangle changes quite a it. The focus shifts to the content targeted directly to the user and, if there is imagery in the results, the users start there. In their test, Gordon said that when personalized search results were given, users were 3x more likely to click on a results and much less likely to click on ads.