Are your adsense adds giving you low returns for each click. It is definably worth checking out installing the google search box on your site. Most people are inevitably going to leave your blog/site at one point at the other. Predominantly they will return to google in their next quest for knowledge.. so why not make it easy for them to access google from you’re site and in return profit from any adverts they click on.  If the search feature on your website is not keeping your users staying at your sight switch it to the google search and profit.