Paid inclusion is a search engine marketing model in which Web site owners pay a search engine company to guarantee their sites will show up in search results. In addition to guaranteeing that a client's Web site will be indexed, paid inclusion may ensure that the search engine's crawler software visits the client's site more frequently, and may also give clients the option to submit information about their pages more often.
According to proponents, such as Yahoo, paid inclusion will help to improve the relevancy of results because it enables the indexing of Web pages that are difficult to access otherwise. Opponents argue that paid inclusion will skew search results, making the ranking less relevant. Although Yahoo and some other practitioners claim that paid inclusion doesn't affect the ranking of a paid link, the mere inclusion of links that would not otherwise be in the results is likely to change the rankings of some other links.
A disclosure statement on the Yahoo site says that some links in search results are paid for; however, paid links are not differentiated in any way from others. For this reason, some opponents claim that paid inclusion amounts to hidden advertising. According to Google co-founder Larry Page, any search result that was paid for should be clearly marked as an ad. Although Google also includes paid-for links, such links are marked as advertising and listed separately from the main search results. The Ask Jeeves search engine site recently discontinued a paid inclusion program similar to Yahoo's, because they found that it led to a greater proliferation of commercial sites, and less relevancy, in search results.