When done properly they are a more unique way to deliver fresh content to your affiliates. Different content, SEO properties, phrases, words, sentence structures and layouts are fed to affiliates usually via RSS feeds for use on blogs but they can actually be used a multitude of ways.

Static feeds are a thing of the past, morphed feeds are the present and future but nothing will ever be as sweet as a hand-made, 100% unique post not used by anyone other than yourself. Just make sure you put some thought into the SEO aspects and keep the frequency up.