Microsoft Access in a multiuser environment is usually an all or nothing affair: either all users have read/write access or no one does. Of course one could always re-create your entire organisation’s group and permissions structure inside the db, but who the heck wants to do that? This morning ESRI mailing list put forth a simple solution:
Give all users full file permissions to the folder (allowing them to create, read and modify the .LDB locking files), but set permissions for the Access database file itself to allow only the GIS section to modify it.
…so simple, now why didn’t I think of that?
Credit goes to Conrad Wyrzykowski for asking the question, and Jim Clunie for the answer.