OSX only (Leopard and above). Apparently Apple added this for time machine’s use, but didn’t expose it in the
Yes, this means you can shoot yourself (and your computer) in the foot (and, err, power supply). However, it has its uses as long as you take care.
Right now I’m using it to serve up content in my web sever that lives outside ~/Sites (because the content is a subfolder in a git repo, and I don’t want to have to keep mirroring it). This can’t be done with symlinks or aliases, as far as I could tell…