I recently discovered a post with a link that referred to another thread than it originally referred to.
I don't know why this happened, nor whether this is caused by human error or something else. The problem of course is that if this were not an isolated case, the use of links to refer to other forum threads (and posts?) would become useless.
See: http://forums.phplist.com/viewtopic.php?t=9306
Besides the increased occurence of posts with links that refer to deleted forum threads and posts, this is an additional worry, and I hope an unfounded one.