Currently, it appears that at least the following, does not actually delete anything from the database:
1) Deleting a ticket
2) Deleting a field
3) Deleting an item
4) Deleting a container
When truly deleting any of these from the application, they should be deleted from the database as well. (The concept of active/inactive as seen in business rules could be expanded to other components to cover for this, similar to how SDE handles this)
Barring that, having a mechanism within the application to purge out deleted database records, columns, and tables would be beneficial. Because if not, things are going to get messy.
You should see my test system's database!