General forum moderation topic-Members deleting thier posts- Can/should we stop them?

Hi everyone,

I hope this the correct forum for advice and thoughts of moderating forums in general.

I have been moderating forums for many years (forums.Winamp.com the biggest). A new-ish (a few years) forum that I mod/admin has grown and now a respectable 100,000 posts.

Now as the size is growing the problems grow too. We have as a current trend of users that have many posts wanting to delete all their posts as they don't like something and want to leave.

Personally I really dislike this "I'm throwing the rattle out of the parm because I do not like xyz."

Not only does it mess up all threads so they are hardly readable but they problem members/soon to be trolls get they day at attention seeking +++++s that they are.

I am after others experiences and thoughts and advice about this.

What are you thoughts on such members?

Is there anything ethically we can do? Stop them deleting there posts?
Has anyone gone from allowing users to delete there posts to a blanket ban on it?
What was the users reaction – too negative?
Is there any legal complications not allowing users to delete their posts?
Do users that ask for there accounts to be deleted have any legal case? - Do we as admin/mod have to delete there posts?

Thoughts and opinions welcomed folks.