As with all things GIS, the answer is "It depends." I have seen performance crippled by thousands of feature datasets with dozens of feature classes in each. Esri training classes make it quite clear that feature datasets exist for cooperative table management associated with geometric networks, topology, or feature linked annotation. It's a common theme in these discussion threads as well. I didn't find any specific "best practice document" but I did find this discussion in the old, old forums.
I would suggest that ease of administration should not be the goal in configuring geodatabases. Best practice for security in databases involves creating one or more database roles for each access paradigm needed ("browsers", "basemap editors", "primary data editors", etc), then granting the roles the appropriate permissions on the feature classes once, and granting users access to the roles. In this way, adding a new user is still simple (grant them the appropriate roles), and you don't need to tie your tables into a monolithic access block.
- V