This feature is required for a cross platform feature of Windows Server: services for mac.
This allows a windows server running on NTFS share to macs via AFP. For this feature to work, the NTFS file system has to support forks, and it has from day one.
And before you ask, is this feature still used? Yes it is I have it running and in use daily on a server in a client that I support.
The main security issue comes when people and applications forget or don't realize that it is there.
There probably should be an option though to include the forks in the total file size or show them in windows explorer.