i never understood the purpose of writing and article for your site, and then copy pasting it in article directories. it just fails to serve a purpose as its uniqueness is lost. you essentially first create a competitive advantage of providing unique information, and then destroy it or cancel it out by syndicating articles…
as far as i’m aware, the trick is to write a couple of versions of the same article, where you would post the original on your website, and the amended versions would be syndicated on article directories…
i believe Aaron Wall on his SEO Book website discusses this issue and even provides links to some programs that generate various articles from the same source. i’m not sure how good are those applications as i havent tried them, but the information written about them and how they work is quite interesting.
hope that helps…