is it safe to have two backed used for the same user?

[lejeczek]

hi everybody

I wonder if it is safe (and wise) to have two passw-user 
databases for the same one user.
I'm thinking,
mail to me via pam
mail to me at this.domain via ldap

whole Maildir would be essentially the same one storage 
target, I see permissions have to be mangled, available to 
write for both vmail and actual uid.

what do you think? Is it how it's done?

regards