When mounting a samba share with nautilus, if the share doesn't require any username/password, it is immediately mounted, otherwise nautilus asks you three things :

username
workgroup
password

Since the server require authentication, there is no situations where the username can be blank. However, mistakes in the workgroup in most situations won't prevent the connexion and some server don't use password, therefore blank workgroup and blank passwords can be tolerated.

At the moment, nautilus accept blank password, however it does not accept blank workgroup : the "Connect" button stay disabled until something is typed in the workgroup box.

For the reasons above, I think that this "policy" could change to make nautilus mount more user friendly for home users that generally don't use workgroups without breaking the functionnality for profesionnal users.

Steps to reproduce :

1. Have a server with a SMB share protected by a password.
2. Open nautilus and type the smb share adress in the adress bar (ex. : smb://192.168.1.100/share)
3. Type your username and password and blank the workgroup field, if it is not already blank.

Result : You can't connect, the button is disabled.

Expected : It should still be possible to click the connect button, as long as there is something in the username field.