Considering the turnover rate in pbp games, lately I've been seeing the appeal of supplying a premade cast of characters as a GM - it seems like it could be a way to keep things consistent even if players cycle in and out. Yet, I know that a major appeal of role playing for many people is constructing your own character.

What are your thoughts on taking over premade or already-played characters? Is it a dealbreaker for you, or does it appeal to you? Why or why not?