Putting files outside the user/home folder Can I put my folders outside the user folder (e.g. on the root of Mac HD), such as personal folder or work folder, where I have many files? The reason I want to do it is that OS X may have performance issues where one folder has too many files (reference), and as a recent Windows switcher, this is more like the partition/disk letter approach to file organizing. I'm the only user of my macbook so there's no privacy issues. When I first copied the files to the root, the os asks for admin password. Will I have issues with permissions if I do that? And in general, what's the potential cons with this and what's special about the home folder?
If you create (or rename) a folder at the root, OS X will ask for your password. This is because you do not own the root folder. Once the folder exists, you can copy (or add) as many files and folders to it without having to enter a password. In terms of permissions, the only difference, between such a folder and your home folder, is the home folder has an Access Control List (ACL). Entering the command ls -led ~ in a terminal window results in listing the home folder's permissions. On my computer running OS X 10.10.4, I get the following output.

Davids-iMac:/ davidanderson$ ls -lde ~
drwxr-xr-x+ 20 davidanderson  staff  680 Aug  6 21:51 /Users/davidanderson
 0: group:everyone deny delete


The ACL is group:everyone deny delete. I assume denying everyone delete permission prevents the deletion of your home folder.

One small point, normally your files are assigned to the group named staff. If you create a folder in the root folder, the group will be wheel instead of staff. You can correct this by typing the command chgrp staff /newfolder after creating the folder. Substitute your folder name for newfolder.