I remember vividly when a user couldn't access his smb drive from Windows because both his printer and also the computer's case came with one of these multi-cardreaders with n slots and the drive letters collided. That's when I learned that smb drive letters don't even come from the "global" pool of drive letters, because, and this is obvious in hindsight, they are a per-user affair (credentials and all that).

I think the concept of drive letters is flawed.