I was writing a scheduled job to move items from a ContentArea in a local block to a ContentArea on the actual page. Copying the items was no problem, but removing them from the old contentarea was more of a challenge. What I expected to work was to call writableClone.LocalBlock.ContentArea.Items.Clear(). This had no effect however. Eventually I resorted to create a temporary list of ContentAreaItems to delete, and then call writableClone.LocalBlock.ContentArea.Items.Remove(contentAreaItemToDelete) for each item.
Shouldn't Items.Clear() have sealed the deal?