seth_wilde - 3:54 pm on Feb 15, 2007 (gmt 0)

The homepage generally has too many different purposes to be able to be optimized to the level that a landing page can be. With landing pages you can focus much more on the individual product/service that your buying traffic for and tweak things that can increase conversion rates but would provide a bad user experience on a home page.
Plus you don't have to worry about seo implication with landing pages.