The idea is when I want to delete a contact list which is still in use (for example linked to a scheduled campaing), the system has to warn me that this contact list is still in use, and it has to ask me if I am sure to want to delete it. Otherwise we will delete the contact list and the campaign will be put in Queued without informing us.
We had the case by deleting by error some contact lists and we have then see that some campaigns were not sent :-(.