Being able to move your content to the top of the page without affecting how the page looks is certainly an advantage. Another optimizing advantage to using absolute positioning is that you aren't limited to placing layers where your visitors can see them. Yet, the engines can. It means that you can put content that you want search engines to see, but not visitors, in this layer. Because the layer is left of the left edge of the browser, there is no way that a visitor can see it unless he or she views the source code.
Browsers only allow people to scroll to the right and down.
So, if you don't want to change the text of your web page but need to add more content, you can add content through layers that only the search engines will see. Using layers, you can add valuable content to the pages and place it at the top of the source code for an added boost in prominence and relevancy. After all, you don't want visitors clicking through and leaving your site through your link lists, so this is a way to solve that problem. You can add additional content in layers that won't affect how your page appears to visitors, yet engines like Inktomi will find and index that content. That way, if a viewer is able to see the layer, it shows up at the bottom of the page and viewers will have to scroll to see the content.