Traditionally, statistics show that most users will trust what they see at the top of a search page. They don't generally question it. That sort of placement alone can give a company a significant advantage, as it can greatly influence and help shape user behavior on a large scale.
A search engine can be a Web site's best friend. A listing near the top of Yahoo or Google could bring more eyeballs to your site than e-mail, banner ads, print media, and even television ads. And the best part is, search engines don't cost you a dime. That being said, getting your listing to the top, where it's most likely to be seen, is not easy.