there is a proposal for improvement:

I would like to have a generic login that I could give to multiple users (family, friends,...).
This login should not be modified by different users: No change to the password, email address, ...

Is it a good idea ?
Could you do this in a future version of zenphoto?

Probably not.

You do have the guest user/passwords to manage access to the front end of your site, so this would be only to manage backend access. For that it really is not a good idea to "mask" identities. Besides, if it is just for family and friends that would not be such a long list of users.

You can use User Groups to have uniform priviledges, etc.

Also, if you do want multiple people to use the same user id, the email, etc. really are not relevant, so it would not matter if they got changed. You could, of course, make a plugin that removes these items from the DOM for a particular user if you really want. I have made a plugin that does disable the capability of setting the watermark if the user is not an administrator. I can provide you with this as an example if you want. It is Javascrpt based.

I did have a different idea--a new right that is the gateway to the user tab. If a user does not have this right he may not access the user tab at all.

This is in the Development nightly tonight. Note that it requires migration to version 4 of the Zenphoto_Authority to enable. There will be a button at the bottom of the user tab to make this migration.

It is another way of answer to my need.
I'll watch it soon.

Thanks