Search engines may consider this as spam. Secondly, you won't be able to make sure that the submittal was accepted. With the amount of traffic they get, sometimes things just go wrong. Thirdly, if you go to their site, they get to sell advertising. It is important to get listed high up in the rankings.
Many searchers only use one or two words to search, and the number of pages returned are phenomenal.
If you're not in the first two pages, forget about being visited. To rank how good a particular page is, search eninges set certain criteria. Many place a lot of emphasis on the page URL and title. The keywords tag should contain all the keywords for your site, in order of most inportant to least important. Also, make sure any text near the top of your page is relevant and contains the keywords.