Here is one. Several years ago, I worked for a company that had an
in-house source control system that worked like this: the 'source' user
owned the current stable version of the source. Each developer made
links to the entire source tree, making hard links for every file.
As a developer edited files, he or she would remove the hard link and
write a private version.
This is like a home-made translucent file system.
This system has its advantages and disadvantages (primary advantage: it
was very economical on disk space). Those aren't important. What is
important is this was a real-life application of hard links to files
that the person making the link doesn't own.
By the way, I favor 'must be owner or super-user to link to a file'
as a mount-time option, with the default being off.
Michael Chastain
mec@shout.net