I noticed this a few days ago. I was trying to set up a development system for Yosemite when I stumbled upon a file named "[" which I'd never seen before. It turns out it's just a copy of the Unix "test" command. During that little sidetrack, I noticed that when I tried to read or get infe on the "[" file the OS would report "input/output error." I assumed there was a bad block on the drive because if their is, that's usually the message you get from the command line. I rebooted from my Mountain Lion volume, which I use as my base OS now and used Scannerz to test the hard drive. Scannerz found nothing wrong - NOTHING! At that point I had just stopped because someone else answered the "[", the drive looked OK, and I thought it was just an oddity. Last night I returned to trying to set up the partition for development and once again, I'm getting the input/output errors, but on everything that's on Yosemite. This is mounted from a Mountain Lion partition. I wrote a little program with super user level authentication and it wasn't allowed to open the file on the Yosemite partition to just read it. It's like the entire drive has been "blocked off" from access. I'm not a security guy, and hadn't really put a lot of time into looking at Yosemite's underlying features. Are these being caused by resource fork settings and can they be changed easily? Right now it's sort of a PIA trying to deal with this thing.