What tiger86 is sugguesting is called keyword stuffing.
"This method is completely outdated and adds no value to rankings today. In particular, Google no longer gives good rankings to pages employing this technique" - wikipedia
Search engines such as Yahoo! actively edit their search results. If you are caught keyword stuffing by an editor or competitor your site might get banned.
This goes for google as well and you will have to re-submit your "user-friendly" site to the search enginer for re-consideration.
So at the end of the day! If you want a good rank. Have the right content. It's that simple.