Navigation replaces recall with recognition: Instead of forcing users to come up with a complex search query, they can recall only a minimum and then use recognition to augment their query with relevant terms.

Search requires knowledge of the search space. In order to formulate a good search query users need to know fairly well what they are searching for. They need to understand the search space and put in the right keywords.

Search increases memory load. Search requires users to recall information from their memory. To come up with a meaningful query, a user must think about attributes that are relevant for his goal and incorporate them in the query. Navigation replaces recall with recognition: Users can recall only a minimum and then use recognition to augment their query with relevant terms.

Search has higher interaction cost than browsing. Search forces users to work more because not only must they come up with a query, but they also must type it.

Site search often works poorly. Even if users are able to come up with a reasonable search string, chances are that the results returned will often be irrelevant. Specialized sites usually do not have the complex algorithms and huge database that big search engines have. Also, most site searches are not well equipped to accommodate typos and abbreviations.

Users have poor search skills and don't know how search works. For example, users, accustomed to the tolerance given by large search engines, tend to expect natural-language searches to work on smaller sites.