Are you planning to have user accounts as files in the shared folder resource? I don't know of any adapter that uses folders/files as resource/accounts for idm users, but you can write one if you'd like. It's just that idm should be the only application reading/writing to that resource (to avoid any variety of files getting in there).
Adi.
I am assuming this is windows shares that you are talking about.
If you are using Active Directory, you could control access to these folders by provisioning to a particular group / ou in AD, whose members have access to these folders through an AD policy.
Ankush
http://www.iamcg.net