It would be nice if samba didn't tell the clients that's not in the valid
users list for a certain share about it.
So lets say the user john is in the valid users list for the "data" share,
while alice isn't.
if john browses the computer, he sees the share, and can access it, if alice
do, it doesn't exist, and if she tries to access it directly, samba acts like
the share doesn't exist.
This would be a nice security feature.
The common way of doing is this is to use included
files in combination with the %U variable.