inactive members

How do you feel about forum owners who will email inactive members and threaten to delete their accounts if they don't become active and post? Is this something you practice on your forum? If yes - has it worked at all?

How do you feel about the idea of purging inactive members? This would mean mass-deleting those who are no longer active. Maybe for a year or more... Is this something you have done, will do, or are current practicing on your forum? What are your advantages and disadvantages of doing it...