One of my friends is going to launch a small article directory (ex: http://ezinearticles.com/) using WP. The site will be hosted on a shared hosting in the beginning and will be moved to a dedicated server in the future.
The site will be open for public registration like any other article directory and each registered user can manage their posts using the WP admin. The user role will be set to Author for all the registered users.
The question is that whether WP is secure enough for an article directory setup like this and whether the registered users can hack/de-stabilize the site even if all the WP security hardening is done. In a nutshell, the main concern is with the open registration.