You can, on a very high level, divide the users who visit corporate public websites into two categories. The first category would be The Pathfinders. Typical for this category is that they try to find a logic structure on the websites in order to find the information they are looking for. They never use the search field on the website.
The other category could be named The Search Generation. They are not so impressed by the website navigation and structure. They normally go direct to the search field and type their query, instead of trying to find it by using the website navigation. The challenges for the corporate websites are to satisfy both these categories.
I am impressed by Volkswagen, who has taken the requirements from category two very serious and placed a search field very centrally on the first page, please visit; www.vw.com