If a user or groups has delete rights then they can cause havoc on a database by deleting documents by mistake. Using soft delete in R5 is one option, but another is to use the querydocumentdelete functionality.
This can be used to prevent users from deleting the documents in the conventional manner but will allow a lotuscript button to email the owner and then delete the document in a more controlled way, or move the document to an archive and then delete the document.