I'm thinking maybe limit the number of posts a user can make in a given period of time. (Say a user can only publish 1 post per 5 minutes?)
Is there such a plugin?
Closest thing out there seems to be: http://www.spaw.it/359/wordpress-plugin-limit-post-creation/, but it only sets a single, hard limit.
I think your best bet is to utilize this Wordpress thread with code to limit number of posts for registered users: http://wordpress.org/support/topic/limit-the-number-of-posts-a-user-can-make?replies=18
You would need to change the
$count_posts var to only count posts made within your time-frame...
Limit Post Creation Per Day plugin seems to provide this functionality.