Why is Admin Approval Needed to Share Folders Between 2 Standard Accounts?

Question

Dear OS X users,
Please give this question due consideration because it's a fundamental question about the underpinnings of OS X which I've asked many people but no one seems to have a good answer. I have 3 accounts on my Mac. They are as follows:
- pete (standard account)
- wanda (standard account)
- mac admin (admin account)
It's logical that if Mac Admin creates a file/folder, he needs to set the permissions for it so that others can read/write to it. But imagine Pete and Wanda collaborate together on a project. Imagine Mac Admin creates a folder called /Swap with read-write permissions for all. Pete then creates a sub-folder without setting any particular permissions and then logs out. Then imagine Wanda logs in and wants to access the Pete's newly created folder. When doing so, an authentication prompt appears asking Wanda to enter an administrator's login details.
*Why doesn't it ask for Pete's authentication details? Why does it need an administrator's login details? Mac Admin has nothing to do with it.*
Now if you extrapolate this scenario to include a business enterprise where you may have lots of groups/teams with members all collaborating. It's ridiculous to involve an administrator for every trivial request of this kind e.g. a file permission change.
Please don't simply recommend sharing via USB or upgrading to Leopard. (I hated Leopard and 'upgraded' back to Tiger). I'm looking more for explanations than workarounds.
Thank you in advance.
MrLinguaFranca.

Answer 1

The short answer, of course, is that admin privileges are not needed (so long as you are the owner).
The long answer is that administrator privileges are required to change the owner of a file or folder, or to change the group of a file or folder (if you are not the owner or aren't a member of that group). To change the permissions on a file, one must be an administrator or the owner of the file.
In your scenario, Pete creates a folder, but forgets to make the folder read-write for others. Wanda is prompted for the administrator password because she doesn't have permission to access the folder until Pete says so. The default behavior on the Mac is to secure the folder.
The reason it doesn't ask for Pete's authentication details is the same as if it were Windows, Linux, Solaris, etc. Wanda is asking permission to override Pete's settings. If Pete wanted Wanda to access the file, he would have done so. So, logically, Wanda requires administrative privilege to supersede Pete's wishes. Wanda should NEVER have to be party to Pete's credentials because doing so compromises Pete's account entirely (nor the administrator's credentials -- if the folder has permissions that deny her access, she needs someone to grant the access, not someone else's credentials so that she can grant access to herself by assuming the role of the other party).
This is different from the case when you are accessing a network share. In that scenario, the connection to the remote machine does not know who's accessing the share and must require authentication to determine who it is dealing with. The correct way to implement network shares would be to have Wanda always authenticate as her self and never use the credentials of another. Once she's logged in as herself, the remote server can determine what she's permitted to access on the basis of her identity and the permissions on the files.
This is how file security works (not just OS X).