I know some people would like to be able to delete or edit their posts. However, I have been burned in the past by others who edited their posts to change the meaning of their post after I had replied, which makes my post appear different. In addition, it is frustrating to spend time replying to something and then find that the original poster deleted the post, taking all of the subsequent posts with it.
Not having the edit/delete function would hopefully keep everyone "honest", knowing that what is posted will stick. :)